The Grandparent's Dilemma at Family Gatherings

My name is Edna and I'm in my late seventies. My family means the world to me, but lately there's this one thing that has been gnawing at me during our gatherings. You see, my son Mike, his wife Carol, and their kids Sarah (12) and Ben (8), always come to these get-togethers. We're a close bunch, or so I thought. I've noticed recently that when the whole family is together for dinner at someone's house, there's this one person who doesn't seem to fit in as well with everyone else anymore. That person used to be me. But now it seems like every time we come around, my grandkids are more interested in each other or playing video games than hanging out with me. I remember the first few times when they were little, and I'd show them how to make paper airplanes or build Lego towers together. Those moments felt so special back then. Now, I find myself sitting quietly on the couch while Sarah and Ben are laughing and teasing each other in the kitchen or the living room. The most recent time this happened was last week when my son Mike's house got a new ping-pong table. Everyone started playing as soon as they arrived, except for me because I felt out of place. Carol suggested that we play too, but honestly, watching them enjoy themselves without me didn't make it seem worth the effort to join in. I'm starting to wonder if this is normal aging or just feeling left behind by everyone else's lives and interests. I don't want anyone to think that I resent my family for their happiness or that I'd begrudge them their fun time together, but sometimes those moments feel like a punch in the gut. Is it selfish of me to miss when they wanted to spend more time with Grandma Edna? Can someone please tell me if this is just an age thing and how do you deal with these feelings? Am I really being the asshole here?