You are legally free to disinherit children if you want to do so. But as you seem to have sensed, it is best to add specific language to your will
that removes all doubt about your intentions. That's because there's a legal rule that holds that if you forgot to mention a child in your will, that child may be entitled to a certain percentage of your estate.
Signify your intention to exclude and override any later allegations of "forgetfulness" in the matter by simply including the notation: "I intentionally leave no property to my son or daughter" -- and add their names.
And stop there. A will is generally not the best place to vent your angst or displeasure with them. But chances are you have done that elsewhere -- either in writing or in conversation.