4 must have hours of baby boomer music?

If you have cable TV most systems have music "stations" with a 60s or 70s niche.

Most of us geezers got weaned on radio (not hearing a whole album at once), so yeah i think the Rhino thing may be a good way to go, (also this way, no one at the party would have to put up w/ a whole album of an artist that they hate). 70's Smash Hits vol. 2 is cool. Spirit in the Sky/ Little Green Bag/ Ride Captain Ride.
PS- I'd try to sneak some Ventures in there.

The best of rick james
Parliament Funkadelic
to name a two
if you are buying cd's just pick your favorite artist.
Most have reissued a "best of..." or "favorites cd" which are ideal for parties. most of which can be obtained on short order from amzon.com. enjoy

- The Byrds
- Bruce Cockburn
- Neil Young
- Joni Mitchell
- Crosby, Stills & Nash
- Anything Boz Scaggs (before Silk Degrees)
- If this is a party where some tend to 'over indulge', throw in some New Riders of the Purple Sage

This might be more of 50+ ..is a 40 year old a baby boomer??

yep. They are just at the cusp. 50+ is the Woodstock generation: the meat and potatoes: Earth Day, Bobby Kennedy, Martin Luther King, The Filmore, The Beatles at Shea, Dallas in '63, Disreali Gears, and on and on. If you don't know what I'm talking about? You may be (statistically) a boomer, but not in my book...