CoEd Shower

My boyfriends mom is generally pretty great, we've some ups and downs but have worked successfully through them. Anyways, she announced as soon as we told her about baby that she was hosting a coEd shower type thing which is totally fine because my bf has a ton of friends and family and its turned into more of a BBQ/shower celebration come this summer. He is very excited about baby and I think it gives him a chance to celebrate with all of them and as well, gives me a chance to meet a few people I've yet to meet that he rants and raves about.
Anyways, my mom is hosting a traditional shower for me so I have saved invites for this shower for my friends minus two of bffs, mom and brothers gf whom I'm very close with, I also made it clear to just bring themselves because it means the world to have them as support there. She keeps insisting I have more people to invite then four ladies but I don't want them there I want them at my moms since she is going through the trouble of hosting one and I would be much better able to visit with the girls at hers and then worry about meeting people at "his". How can I politely tell her I feel as this is more for her and his family and friends then for me so I want to reserve those invites for my other shower over hers. Please keep in mind I am so very grateful for both and that people are eager to attend. She insisted on having the coEd one and there was no way for me to get around it so I'm just trying to embrace it although I feel slightly awkward about putting a registry on a "BBQ".