I shot a birthday party of a 5 year old where about 150 people came. I had a helluva good time. You catch the moment. get a good flash, use auto if you've got it, and chase kids and capture the excitement. I got some truly amazing shots out of that shoot. Here is one of my favorites:

there was pinata bashing and all kinds of insane actions. the age of participants ranged from 8 months to 80+ years old. Capturing the heart is really what its about. Everyone loves the pictures. It's not a wedding. Its an action movie with cake crumbs and wrapping paper!
Here's a bunch of shots -- they are not well focused or properly lit -- I'm no professional, but a lil kid's birthday party is about fun and action and heart. That, I did get.
grandma and her baby girl

Daddy's lil gurl
[img]http://highlandgodz.com/highlandgodz_images/savanna%27s%20b-day%20edits%20031.jpg[img]
it helps when the birthday girl is the cutest thing on the planet

aaaaaaaaaaw

blurs are fine. it's the excitement of opening presents that counts.

brutalizing Cindarella is apparently OK at 5 year old birthday parties.
anyway, I had a lot of fun at that party. And so did everyone else.
the main thing is to GET THE BIRTHDAY KID'S FACE IN FOCUS AT LEAST 6 TIMES
get a lot of shots of the interaction. It's not hard to come up with gems at moments like these. With three year olds, its even more insane. If you can, have someone good with a video camera to back you up. People don't care about professional at these times. They want fun.
