Can't invite my church

So my mom seemed to get upset because I'm planning my wedding and I'm not going to be inviting people from church. The venue we are choosing is up to 80 people. I really just want a small venue. She's wanting me to do an announcement but I don't want to risk people show up and not having enough room. Mind you it will be me and my fiancé funding it all. It's nothing personal at all. They've been there for my family a lot and I'm now starting to feel a bit guilty. I don't want to hurt their feelings but it would be even more hurtful to say "hey I know we invited you but turns out we don't have enough room so you can't come". I feel like the church will understand but my mom seems bothered.