I am around your age, and my 10 year reunion had its own domain name and website (still up - not sure who is paying for it or hosting), but my most recent reunion (20 year) was only on Facebook, and since I have never had a Facebook account, I did not find out until about a week beforehand (second-hand from a friend who was not attending).
Please be aware, this is a cohort that has mostly been together since elementary/middle school, learned Logowriter together, and had an HTML CD-ROM yearbook.
Facebook has made everybody lazy and cheapened our relationships.