I haven't heard of adult games either at a kids party, but some games already mentioned sound fun.
Another idea that I played at a baby shower - get 6 clean diapers. Get 6 different snack-sized chocolate candy bars. Put a candy bar in a diaper, then in the microwave a little bit, so the candy bar melts a little. Maybe mash it up. Label the diapers numbers 1-6. On a paper, the adults number 1-6 and they must identify (through touching, or by opening the diaper and sniffing) each candy bar. The winner gets a prize. This game is hilarious b/c a whole bunch of adults are sitting around with their noses up to these brown yucky-looking diapers. Makes for a good laugh and a good picture or two.
If the adults coming don't have kids of their own, another game might be where they have to finish the lyric to the common kid song or fiill in the blank on a common kid story.
Another idea - have a taste test where the adults have to correctly identify the baby food! Gross, but fun!