Is there a way to see your entire mafia's wishlists at once instead of having to check everyone's?

Unfortunately, no, the only way to see what people are looking for is to either manually go to their game profile, or see their wishlist in your news feed if they post it. :(

I totally agree that the current implementation is pretty lacking -- I have a very hard time finding people who need my excess items. Maybe someday Zynga will make it better (haha!) or someone will come up with a clever solution. I'll keep my fingers crossed!