My Dd had her parter at Wonderscope a year ago when she turned 5. It was a blast and reasonably priced -- and the food/drink is included. (NOt a fancy cake -- cupcakes and apple juice....But we had a hard time getting everyone to stop playing long enough to eat anyway)
Another benefit of Wonderscope is that parents can stay and you don't have to pay anything for that. We had 17 kiddos at my dd's party and the extra parents allowed us to divide into groups in the different rooms - as there were different paces/interests.
The only negative I have to say is that it was a bit chaotic the day we had our party. There were too many parties ---BUT that was b/c the previous weekend had been a snow storm and several parties from that weekend were rescheduled into the weekend of our party. That said, aside from being crowded it went very smoothly.
I would say that for the money it is one of the most affordable and high value parties. With the group of kids I invited I think NOTHING would have stopped them from coming to the party. One mother got up early to try and arrange a ride for some of her kids when one of them got sick and couldn't attend. (And Wonderscope had no problem w/ this little girl's brothers taking a cupcake home to their sick sister her was 'really sad' she couldn't come.)
It is a place kids will want to come.