I need advice

Ok, here is the situation:
My parents are paying for the entire wedding (300 ppl). My future inlaws are paying for the rehersal dinner. My mom was under the assumption that the wedding party and OOT guests are invited. When my mom approached my FMIL, she told my mom that she did not want to invite OOT guests because that would make the guest list for the RD that much bigger. Now my mom didn't really say anything. Well, tonight she came home and was in a bad mood and made a comment leading to believe that she was really mad about it. NOW, my question is, what do I do???
Here my parents are inviting all of these people, over 100 PPL for my FH's side and the OOT people can't come for dinner. UUUUGGGGG. Any advice???
Thanks

I totally sympathize with you...my parents are footing the bill for the wedding too and whether I'm having a rehearsal dinner is still up in the air. FMIL doesn't seem to think it's necessary. FH insists that his dad is aware of protocol but here it is 2 1/2 months to go and no mention of the RD. My mother has already expressed that if they're not throwing the RD then she is NOT inviting their side to the wedding. I am predicting DISASTER. My suggestion is to have your FH sit down and explain that OOT guest need to be invited as a matter of etiquette.

Easier said than done. Their family is all boys, so they have no idea. I am going to try though, this is a disaster waiting to happen, I can feel it.
Like we don't have enpugh to do