Should we bring my 100 year-old grandmother to a family reunion?

A few  details  would help me answer your question. First of all, does your grandmother want to go to the reunion? Secondly, does she have many other opportunities to see family members? Finally, how long and taxing will the trip be?

If  your grandmother wants to go to the reunion and has few chances to see family members, then I think you should bring her along -- unless the trip will be too much for her. At 100 years old, she isn't going to have  many opportunities enjoy such get-to-gethers. Even if she's weak and cannot participate in many activities, she will still enjoy seeing everyone, even if she spends a lot of the time resting and watching her great grandchildren play, for example.  She's bound to be cheered by seeing far-flung family members and basking in the warmth and love of relatives.

If you're concerned that you'll bear the burden of caring for your grandmother during the reunion, enlist other family to help ahead of time. If you have the means, you could even hire a companion to help you care for her during the trip.

If your grandmother doesn't want to go to the reunion, I wouldn't push her to do so. Respect her sense of her own limits, and remind other family members to do the same. You can help her enjoy the event even if she can't make it, by sharing photos and videos when you get home.

If she turned 100 this year (or 101, for that matter) is there a plan to celebrate her birthday at the family reunion?  It's important to honor such milestones in lives of our elders, and to let them know how much we respect and appreciate them. Even if she doesn't attend the event, you can have everyone sign a card, make a home made gift, or help create a photo collage that will help her feel part of the reunion, whether she's there or not.