You may have found an idea already but I thought I'd just add my 2 cents!
We just had my daughter's 6th birthday at a ceramics place. They paint a piece of pottery and then it gets "fired" and you'd pick all the kids' pieces up in about a week. I don't know if your group is too young for that but for the 6 year olds it worked out great!
They had a special party room and we did cake, ice cream and presents. We live in Tomball but I'm sure if you googled "ceramics or pottery studios" they would have some.