He is not diagnosed but showing a lot of signs of dementia, including anger and inappropriate behavior. We've found that spending short times with him — a simple meal, a trip to the store — are the only ways we can handle him. (He lives in AL nearby)
My daughter is graduating high school and he keeps saying he wants to come, but it's a huge school so it's going to be at a local college stadium and it will be several hours long. He has a way of making things all about him — this was true before his decline — and I just don't want to deal with it. It's my daughter's day, and we want to celebrate her. My sister will be coming from out of town so I was thinking of having a dinner the night before, something more manageable, but I know he will be upset. And yet, I can't be his caretaker on this day. I want to be there for my kid! I want to take a lot of pictures and cheer and enjoy it. Is that wrong?
Have fun and allow yourself that opportunity.
Have a smaller, separate celebration with your daughter & Grandpa.
You can and should feel sad that your dad is so diminished. But you didn't cause this decline, so no guilt.
Have a special event before and/or after that will be manageable for dad. If he gets upset, say "sorry, Dad, I can't manage the logistics".
Just tune out his grumbling after that.