I do not know your grandmother's mental and physical capacities, but at age 88, I doubt she could maintain her home (or her self) without your family's regular assistance. Life at her house wouldn't be as good for her (or anyone else) without your DAILY efforts.
Your grandmother may not understand that you are willing to do this for HER, but are UNwilling to do it for THE MIDWESTERNERS. There is no more point explaining this to your grandmother than there is "explaining it" to the "Midwesterners."
There are a few things, however, which may discourage the "Midwesterners'" desire for a "vacation" at your and your grandmother's mutual expense, while SIMULTANEOUSLY preparing for future care-taking needs which will inevitably arise as your grandmother ages.
Before suggesting an approach, I'd like to point out you have THREE ISSUES. One is THE VISITING - and the imposition upon your grandmother's generosity with respect to her time, energy, and resources. Another is THE CLEANING - and the quite obvious imposition on YOUR time, energy and possibly resources. Lastly, REASONS behind it all, or "What is wrong with the Big Picture?"
THE VISITING (How to Discourage It)
1) Call your aunt when your grandmother is sick and ask her to come and take care of her.
2) Call your aunt when YOU are sick, and ask her to come clean for your grandmother.
3) Plan a family vacation and call your aunt to come and stay with your grandmother while you are gone (and clean for her...)
4) Call your aunt and tell her you are excited to be seeing her because you and your (boyfriend, husband, friends) are going to be staying at her house (swear you won't be any bother...) for a few days the following week while you visit (anybody).
5) Just "SHOW UP" at HER HOUSE!
6) Next time they DROP IN for a visit, HAVE YOUR BAGS PACKED AND TAKE YOUR GRANDMOTHER AWAY FOR THE WEEKEND.
7) Next time they call Grandma to arrange a visit, call and cancel because you have an outing planned that Grandma forgot.
8) See Approach #2 below.
9) Before they come put a BIG sign over your Grandmum's door "FREE LODGING"
THE CLEANING (Ways to Handle It)
Since you say your aunt and her family do not appear to have money worries, I would do one of the two following:
Before the next "visit," call your aunt (it will be less inflammatory if you call, rather than one of your parents) and "chat" a tiny bit. Talk about your grandmother a little, the weather... If she doesn't ask about YOU (and she may just be that insensitive,) bring up whatever is going on in your own life - including the "news" that you've developed a strain in your dominant hand and wrist... - Tell her it's probably from being on the computer too much, but it really hurts. THEN tell her that's one of the reasons you've called. Ask when she thinks they are coming to visit next. Tell her you HATE TO ASK, but since your wrist is SO STRAINED, you don't think you'll be able to handle the "post-visit" clean-up you normally do.
She'll likely feign shock and tell you they NEVER leave the house a mess. YOU will say "You know what a stickler Grandma is."
Tell her "in confidence" your grandmother doesn't like it to be known, but YOU have been helping with her housework for YEARS..."
THEN, ASK HER IF SHE'D PLEASE, and - promise you'll arrange it and oversee all the work, PAY TO HAVE A CLEANING SERVICE COME IN AFTER THEY GO... Have a prepared estimate in hand, ready to give her over the phone.
This approach, the most tactful, may also require some involvement from your grandmother or mother if your aunt calls either.
BEFORE THEY COME:
Do NOT clean for at least several days before they come.
Do NOT be available to HELP your grandmother prepare for the visit. No making of beds, shopping for groceries, emptying of drawers or making space in closets.
DO REMOVE any groceries, supplies, toilet paper, etc. you or your parents have bought for your grandmother - EVEN IF SHE PAID FOR IT.
(Box it and take it home until they leave.)
Do NOT accommodate their impending visit in ANY way.
SAME for BOTH your parents!
If your grandmother HAS A CAR, put it in the shop for a tune-up right before they come OR
PUT YOUR CAR IN THE SHOP and borrow your grandmother's.
TAKE HOME ALL THE BED LINENS so you can clean and iron them.
WHILE THEY ARE THERE:
CLEAN CONSTANTLY. As much as you can.
While you clean MOVE THEIR BELONGINGS FROM ALL AROUND THE HOUSE AND PUT THEM INTO ONE ROOM. (This includes personal items and valuables.)
COLLECT their belongings in GARBAGE BAGS as you go from room to room. (WHILE THEY WATCH)
Do NOT stop visiting your grandmother DAILY, as you and your parents usually do.
RUN THE VACUUM CLEANER especially when they are talking or WATCHING TV.
TAKE YOUR GRANDMOTHER OUT TO EAT while they are there and DO NOT INVITE THEM.
OR DO INVITE THEM and INSIST THAT THEY TREAT.
DISCONNECT THE POWER TO THE WASHING MACHINE. (Use the circuit breaker)
IF THERE ARE LARGE AREA RUGS ON THE FLOORS take them all out for cleaning AT THE SAME TIME.
OCCASIONALLY, covertly go and DISCONNECT the TV CABLE - in the basement or garage. (not behind the TV)
PLAY LOUD DISCO or RAP MUSIC while you clean.
MOAN and GROAN when doing a tough job.
WASH GRANDMA'S WINDOWS and ASK THEM TO HELP!
Ditto FOR HEAVY YARD WORK.
Ditto for WAXING HER CAR... HER FLOORS... WASHING THE KITCHEN CEILING.
When any of them are using a glass or cup, plate, bowl, take it out of their hands right before they finish drinking/ eating.
Grandma, being of advanced age, could need live-in care, even if just for a brief illness, at any time. To prepare for this, I would confide in your aunt how glad you are that she is there so you can "SHOW HER THE ROPES..." so she is ready "for when the time comes that she needs to do a turn providing 'live-in' assistance."
REASONS for Bizarre RELATIVES:
(A Little Perspective Can Go a Long Way toward Figuring Someone Out)
I'd venture that your aunt is concerned about your grandmother's ever-shortening life expectancy, feels the need to "be with" her mother as much as she can while she can, feels guilty for living so far away, and is trying to make up for it with "regular visits." She may worry, too, about your family's apparent closeness to your grandmother and feel your "good deeds" have underlying ulterior motives. Think of it from her perspective and it's almost reasonable.
Visiting "Mother's house" may be the only way your aunt thinks she can monitor her mother's state of mind, the "inventory" of her mother's personal possessions, and the contents of "the house." It gives her - especially with the general hubbub such a mob of visitors creates - ample opportunity to investigate your grandmother's financial affairs and the status of her "holdings." Some people worry about these things, especially if their relationships with siblings are not close or have not been good. So, a combination of factors is probably the reason for the mob scene, and for the frequency of these visits.
Clearly, this aspect of the situation (your grandmother's estate/ business) is a matter for your mother or father to handle, depending on whose mother it is. Is there clear understanding in the family with regard to important issues? Has an executor been named for her will? Does she have a will? Does she have a Durable Power of Attorney in place - for finances? for health care and end-of-life issues? Does she even have an attorney? Has she expressed preferences with respect to her final arrangements? Written an obituary? All these things need to be done sooner or later, and if they are NOT done, now is the time. If these items HAVE BEEN HANDLED, it is a different problem.
Money may not BE a factor. Your aunt may have a sick need to possess her mother's "love." She could be jealous of how close your family is to "her mother." Some people, insecure as children, NEVER grow out of it. The fact that your grandmother tolerates your aunt's behaviour (and she does, even though she may complain to you) could mean that SHE understands some underlying reason for your aunt's need... which you can't. But, ALL these people, INCLUDING YOUR AUNT, are clueless, obviously.
I'll venture a guess that you live in a "coastal area," "sunshine state," or other locale with "high recreational appeal"... major city? : - )
You need new relatives...