I used to have occasional dreams about going back to high school...not for a reunion, just going back to that town and finding myself at the school. Sometimes I'd be concerned about my locker...could I remember the combination, or I'd go to the locker and find some of my stuff still in it...but it would always end when I went outside and walked to a grassy area behind the Admin building that overlooked the sports fields...which is where graduation ceremonies were held.
I figured out that things that I had learned or acquired (habits, good and bad) were rooted in the time I was in school there. I never had to go to class in my dreams so that meant the time for learning was past and that walking out and seeing the place where graduation was held was telling me it was over, I graduated from that time in my life and I needed to take the lessons that benefited me and leave the rest behind.
I considered going to some of the class reunions but the people I would wanted to see wouldn't have been there, and the rest...no.
My sister (4 years older) did go back to a 20th reunion, my husband and I met up with her and her daughter in the town where we had grown up.
I knew she felt she had something to prove but ultimately when she went to the dinner, she took a look at all the people and realized they meant nothing to her, and they left.
At least we 4 had good times before then...and if it took that reunion to free her from her past, it was a good thing...

If you have another reunion dream, if people are involved, try asking them what they're doing now. I'm still in touch with a few people from that time and sharing old memories isn't all the friendships are about, but we still talk about some things...