Wife's parents should be footing a great deal of the bill if you want to be traditional. Husband's family typically overs the rehearsal dinner, drinks at the reception, wedding party flowers and grrom's tux. Wife's parents typically cover the rest (dress, venue, food, hotel, etc.) Wife/Groom typically cover the photo, music, etc.

I don't think you are out of line...if you struck a deal with them awhile ago I would politely bring that up. If they really are hard for money then negotiate but I wouldn't let them flake...also be cause on both argument sides since they will be your in-laws.