Once, unless they are shy, in which case I let them off the hook. I also bring them up at the end to take a chorus of cheers, and present them with a special balloon.

I use other kids the rest of the time. Spread the fun.

2-3 times. Today the little sweetie asked if I could use her little brother! For the most part, I use only the birthday child. It's their day. I can't use everyone at the party, so a good compromise is to use only the birthday child.

First if I can get everyone up to help out. I always let the birthday child pick helpers at first then make sure everyone gets a chance to help. I give away small magical gifts too. The birthday child at the end of the show for a larger effect, i.e., suspension chair or the like. Using as many children as possible with the birthday child getting the applause and using their name as a magic word, gets me a lot of other bookings from their friends. The magic wasn't possible except for the birthday child, the parents love it too (the siblings get jealous so I come back for their birthdays too).