I took Fudgie when he was a bit over 2 and he had a great time. I think he would have been ok at a younger age, and there were younger kids with us.
The big thing will be, how stable is your kid? A strong walker and runner? Also, is the place going to be open to the public at the same time or will it be just the bday party people (who may be more careful around your kid).
HTH :)