Reddit mentions of CLOWN ACT OMNIBUS - Guide to Clowning

Here's a classic - Dr Dropo's Juggling Buffonery.

https://www.amazon.com/Dropos-Juggling-Buffoonery-Bruce-Fife/dp/0941599051

If you're looking for inspiration in general, check this out - The Clown Omnibus.

https://www.amazon.com/CLOWN-ACT-OMNIBUS-Guide-Clowning-ebook/dp/B00B2E1YVC/ref=mp_s_a_1_1?ie=UTF8&qid=1525205604&sr=8-1&pi=AC_SX236_SY340_FMwebp_QL65&keywords=clown+omnibus&dpPl=1&dpID=51VXTd9cZ0L&ref=plSrch

I'm not going to say that any of the material in these are particularly good, but if you're looking for examples of acts that have apparently tested well in front of kid audiences, these are probably a good start.

Note about kids shows (with the added note that I'm not a kids' entertainer) - when you do these kinds of gigs, you're usually also performing for the parents - even if it doesn't seem like they're paying much attention. If you're looking to break into the kids/birthday/whatever market, those half-watching parents are the ones who'll refer you to others. Being polished and having a plan might not make a difference in the kids' enjoyment, but it'll have an impact on your success in the long run.