Haven't replied because, well, lots of reasons including I probably won't be going in April because of my wedding. The Shoe Addict would be upset if I missed that one.
Anyway, here are some ideas if it were me. A YMCA or school gym. Lots of room. All of them are eager to get money.
Town hall or meeting rooms. Here we could rent out a decent size Bingo hall no problem. I happen to have one in my development that gets used for birthday parties a lot.
A back room of a restaurant. If you buy their fod they give you guys the space. That includes McDonalds and their playland.