4 must have hours of baby boomer music?

This may be better for late 40's early 50's boomers but, assuming you have access to a multidisc player you can put on random shuffle, for a "fun" mix, I might try:

Beach Boys - Endless Summer (or one of the other compilations)

Rolling Stones - Forty Licks (CD 1)

Diana Ross & the Supremes - (one of the greatest hits compilations)

Forrest Gump Soundtrack - (CD 2) (alternatively the Big Chill soundtrack)

Bee Gees - (one of the greatest hits compilations)

6th disc - Creedence Clearwater - Anthology

Going somewhat younger:
Tom Petty, Police, Paul McCartney, Paul Simon, and Michael Jackson greatest hits compilations. (Sixth disc - Blondie?)

Of course, if you have an iPod, you can pull together a much greater mix.

I assume, by the way, that this is a non-audiophile "fun housewarming party rather than an audiophile "critical listening" [and not necessarlily less fun] party.

yes, just some fun listening...not an audiophooish party..

I'm going on 40 and whenever we have friends over the following always work: James Brown, Marvin Gaye, Al Green, Ray Charles. Have fun.