Re: Is this man playing games?
I'm somewhat older than you, and I've buried both parents. In their declining years, it was really really hard for me to make any plans. I'm afraid I wasn't much fun to be around, either. There were times everything seemed to be going fine, and one would slip, and we were back to the hospital. It was stressful to watch my parents go through that, and it was hard to switch off that sadness and get back to my life.
Don't aim for things as big as Vegas. Tell him you don't need huge plans or presents. If his adopted child is old enough to stay with Grandma for an evening, and call if there's trouble, then he can just pick you up for dinner and a movie. Say "We'll start with that, and see how it goes. Okay?"