D.B.
Your daughter isn't going to understand one thing about this day, so forget the zoo and places where people need to pay an entrance fee. That's still expensive - you're just passing the costs on to your guests, which isn't so polite an idea. 30 people will be way too stimulating for her so plan on her being cranky and absolutely not enjoying everyone cooing over her. The only thing you can do is what others have suggested - a church, YMCA where someone is a member, a condo with a community room, etc. You'll have to plan on bringing in toys for your daughter and other children - otherwise, what will they do? If family members don't mind a pot luck, that's fine. Otherwise do what you can afford - coffee & cake and some other desserts, or a simple buffet. Restaurants get busy in December and they can charge whatever they want because there's greater demand.
I think it's a good idea to scale back birthday extravaganzas for small children - they don't get it! And as they get older, do you really want to be throwing birthday parties for 25 kids and then getting 25 invitations throughout the year which will tie up every weekend and have you constantly buying gifts? It's great to celebrate our kids' birthdays but it has to be reasonable and based on their age.
Good luck.