OP, I think your DMIL is over the top expecting you to participate in this debacle.
Frankly, there's no way in hades that I'd participate in a fund raiser for the engaged couple--especially as they are known to be irresponsible with their money. It's just classless beyond belief
RE: Jack and Jills (or Stag and Does)---these are used in my area as a fund raising method for various reasons. I.e., medical expenses, scholorship fund for orphan, repair bills for a down-on-their-luck family are some that I've seen and generally I have no problem with fund raising this way. But for a WEDDING??? No way!!
Frankly, there's no way in hades that I'd participate in a fund raiser for the engaged couple--especially as they are known to be irresponsible with their money. It's just classless beyond belief
RE: Jack and Jills (or Stag and Does)---these are used in my area as a fund raising method for various reasons. I.e., medical expenses, scholorship fund for orphan, repair bills for a down-on-their-luck family are some that I've seen and generally I have no problem with fund raising this way. But for a WEDDING??? No way!!
And to think the tackiest thing I had to deal with at my wedding was whether to include the chicken dance or not! 

Just kidding...do what YOU want...
. All of the family know the money issues they have. They "borrow" money from MIL every week, yet they have money to buy wine and smoke. They told grandma (who they rent from) they can't afford the rent, yet she goes get her nails and hair done every other week, I mean I could tell story after story. The latest was spend over $600 on her birthday gift
It's been a lot of years though since the last one & I vaguely remember it being just the immediate family that provided all the food, not the entire guest list.