I'm surprised nobody has mentioned David Kaye (http://www.sillymagic.com/
) Maybe he's not as well-known as these others (which I've actually never heard of), but he's very good.
His book "Kids Show Kliff Notes" is great (as is his lecture on the topic) and he has some other books/lecture notes on his website (under Magic Shop) that seem to be pretty good as well.
As far as Birthday Parties, I learned quite a bit from Trixie Bond (http://www.trixiebond.com
) I know she does lectures and those sorts of things. However, she doesn't seem to have any of her books/notes for sale on her website for some reason. There's a link you can use to contact her (go under "For Magicians") -- maybe you can get some info. from her that way.