I know exactly how this feels, and it's a hard situation to deal with.
Why don't you tell your MIL that she can plan the shower and everything, and let her think she's running the show, it seems as though your mother isn't jumping at the chance to throw one. So let the MIL have her way, and then if your mom still wants to throw one, let her and dont tell the MIL- you win either way. As far as schooling goes - tell her it's a decision between you and your hubby. If you can't stand up to her - tell your hubby to talk to your MIL like it's really bothering him and that should make her back off.
honestly i would LOVE it if someone pushed into paying for anything! i am willing to put my negative feelings aside as long as it is benefiting my kids in ANY way. it might sound selfish of me but as long as my kids are benefitting in any way i am okay with giving up some control. and a private catholic school education is something i want for my kids but i know i won't be able to afford ever.
My husband tells my MIL everything! I've ask him to stop and that didn't take place so now I have to keep my business to myself and not tell my husband! It's kinda funny because I'm taking his and her control and power away. I hoped that I would have a good marriage this time but mamma boy's are the worst. One time I ask him why he keeps sucking on her tit and he took it sexual and I know he knows better! He is ruining our marriage because he's a titty sucker!