i agree, lisa, moms technically aren't supposed to plan. my sis gave my mom and mil a job, and that was it.
i'd definitely talk to fsil about it more...tell her it's NOT what you want, and it's supposed to be your day. OR, would it be possible to have your mom talk to one of them? my mother had to talk to mil AND fil about shower related etiquette. she did it so that i wouldn't have to be the bad guy.