A baby shower, like a bridal shower, is usually an adult occasion. Other than nursing infants, children generally aren't included.
No one needs to get a sitter, they just leave the kids home with daddy (or another friend or family member) for a few hours that day.
Of course if you WANT 30 kids at your shower then I guess that's your business, but it's just not something I have ever seen done, and of course it would be much easier to find a place to have it.
Who will be entertaining and supervising the children during that time, while you and your friends are playing games, visiting and opening gifts? That's something else you'll need to think about.
I love my kids but I also look forward to attending events where I can spend some fun quality time with my girlfriends. Even if my kids were invited I would leave them home with my husband, much more fun for everyone!