do a movie themed party for him--with a focus on movies from the 60s. lots of popcorn, twizzlers, coke, orange soda, junior mints, etc. rent a few old movies from then and have them on the tube in the background, and encourage folks to dress the time--i remember having the "baldies and greasers", the "arts crowd", the beginnings of the hippies, the ROTC kids...there are lots of possibilities.
and neena, your idea about the scavenger hunt is brilliant! i hadn't read the whole thread--but you're right--this sounds like fun. my hubby will be 70 this year--could be a good start planning for his!