Have a good look through
http://www.kidshowmagic.co.uk. They have DVDs and books on this exact subject.
I can highly recommend Bill Abbott's DVDs, and I've also got one by Tim Shoesmith, called 'Magic Without Mayhem.' In my opinion, it's not exactly for me, but you may find it useful.
Also, do a search for Mark Leveridge - he has a lot of published stuff on kids parties and so on, including games, magic and everything. Not got any of his stuff yet, but it's on my wanted list.
If I can help in any way, feel free to PM me.