So, let me see if I get this right...

Your parents are demanding that they pay, but won't pay for the type of reception you want.

That seems... odd? Why are they against it? Why are they so adamant you don't contribute?

I posted my "bit" before, but we are actually having two receptions. The first one my parents are paying for, and it will be a cocktail and hors d'oeurves reception (sounds similar to cake and champagne that your parents want). It will be calm, serene, and fancy. It'll be mostly family and some close friends. My parents certainly didn't demand it be this way, but it seemed to make the most sense within our budget and wanting to keep it semi-small (Family + Close friends... about 130)

Saturday night, FH and I have having a PAR-TAY.... so that all of my sisters and his brothers and all of our other friends can come and just have a good time. We're paying for that one, since neither our parents nor us felt it was fair to have them pay for two receptions. This one will be more like... who knows... 300 people? More? But it will be casual and fun and probably rather rowdy. We're not doing anything fancy, just renting a park pavillion or something and serving burgers, subs, and beer, etc.

Could an option like that work for you?