I've been to a few school reunions (mine and dh's). Imo, they can be fun, depending on who shows up. Better if some good friends from the past are there. Since your dh already keeps up with his favorites and most of them aren't going, it might not be so great.
However, I find it can be interesting to see what has become of people - the bloke who was always going to be a lawyer but became a teacher, the girl who was "never getting married" but now is married 35 years with 5 kids, etc. If it's one's spouse's reunion (as this one is), it can be fun to see who he hung out with and hear their view of "who" he was back then.
As for "bragging," I think some of that is in the ear of the beholder. The fact that someone tells you what they've done with their life and it sounds good, doesn't necessarily mean they're boasting. If they go on and on about how much money or power they have, how successful their ac are, etc. then that's a different story. Also, would one want to hear a run down of all their troubles? I don't think so.
I'm glad you're leaving the decision up to dh. That's the way to go, imo.