Hey, Meraviglioso. Your parents' preoccupation with "stuff" is their deal, not yours. You don't have to be pulled into that orbit. Just bring yourself, a small gift, and a willing spirit. The really, really nice thing about family visits is they are in the rear view mirror before you know it.
Don't drink. I know you don't plan to, but definitely don't. Remember to breathe. If they have a dog, walk it, or just go out onto the deck/porch/patio for some fresh air from time to time. It is amazing what a little breather from the claustrophobic tension of family gatherings brings. Are there any friends or neighbors there with whom you feel simpatico? Chat with them. Good luck. Let us know how it went.