I actually see where you are coming from. Maybe it's a Wisconsin thing because around here most of the weddings are still paid by the parents. Although, times are changing and I think more and more couples are helping out. Perhaps it's because the average age of brides is getting older so we can actually afford to pay for it ourselves? I don't know.
None the less, I was in the same prediciment that you are in. My mom and dad made it quite clear what they were giving us... however his parents never did. And in the end, them coming to the wedding was their contribution. And that's FINE, and great! But, it would have been nice to know and I wish I would have asked. But, since I didn't know, I budgeted for everything, kept costs low, and then made sure that I could pay for everything if it came to that.
So, in conclusion of this LONG response... talk with your mom and then plan a low cost wedding that you and your FI can afford and will love.