Like any performance, it's not the effects that matter but the presentation. Make things as silly and as fun as you can. One of my favourites when I'm performing for my nephews is to produce green boggey sponge balls from my nose and yellow ear wax sponge balls for their ears, it sounds disgusting but they love it. I've also got a russian roulette routine using eggs, 4 hard boiled ones and 1 raw one. 4 kids and me all pick an egg and break it over our heads, guess who ends up breaking the raw egg on her head?

Get the kids involved and if yoou can give them all something to take away then that's even better. Balloon dogs or even just a little plastic wand will go down well.