For entertainment besides the play equipment we had bean bag style games (cut holes in cardboard, buckets at different lengths) and also a sheet of contact taped between two poles for kids to stick different things on - had cardboard shapes, feathers, glitter, pom poms, popsicle sticks etc and that was very popular and left a great take home piece for DD1 from her friends (just attach another length of contact on the other side).
What an awesome idea and a beautiful way for your DD to remember her birthday party!

DS1 had his first kid orientated birthday party when he was 4 and we held it at a play cafe. Hectic yes, expensive, yes but no mess which was great!