T.H.
Is this a baby shower for you or for someone else?
I would try looking at community centers near you. You can rent a room for pretty cheap and then just bring in all the food/games. Restaurants are a good idea, but many of them can be expensive. I know First Watch, which has good brunch and fairly reasonable prices, also has a private room to rent and they would obviously provide the food, but it is my opinion that if you're going to have it a restaurant you should be picking up the tab for the entire party.
There are lots of venues in the KC area, but I'm not sure how affordable some of them are! I can't exactly remember the name of it, but there is a cute Victorian Tea Room in Prairie Village right about 83rd and Mission and it is adorable! I looked into having a birthday party there and it was cute. I don't think they do food but they let you bring it in.