You are WRONG IGOR!!! Kids will try to see why the effect happens. They want to catch you. Even if you're perfect and don't flash they will yell out what the THINK is the secret. Their attention span is very short and you have to keep the show moving for 30 minutes. That is HARD to do with a bunch of kids, especially if their ages are different. Because if you have effects set up for the younger kids, the older kids get bored. Then if you have things that are for the older kids, the young ones go nuts on you.
Paddy, I agree with you. However, I have learned that it is most beneficial to pack a few things that will be entertaining to everyone. Back in the day, when I did birthday parties, I would always include some effects that the teenagers would enjoy and a few effects spread throughout the show that the adults would like, too. you have to remember that you're not just entertaining the little kids, but everyone
at the party. If you do that, you will get repeat bookings and LOTS of referrals.