Kids are more likely to agree to have magic performed, so you really should not focus on approaching them, but rather, how to deal with them.
Have many tricks prepared--more so than normal--because they are likely to beg for more and will be disappointed if you cannot pull through.
Pay special attention to your vocabulary. It may seem like common knowledge not to use profanity, but you would be surprised how easy it is to forget.
Tailor the routine to consist of more "cool" or "neato!" tricks. Mystifying tricks will fly over their heads.
When performing for children, tricks considered childish or "beneath you" are exactly what is needed.
Be prepared to hear innocent, and often correct assumptions as to how you accomplished the trick. Do not fret, though, because they usually never know they are right.