I would say that BB is probably your best bet. It is more wild and has more fun things to do. It has a large play area for the smaller folk and some very cool slides for the 12 year old and adults. It is NOT very shady though. If you go to BB, make sure you have plenty of suntan lotion to put on. The sun against the snow capped mountain mixed with the water is a pretty good degree for burning.
Typhoon Lagoon is more layed back and usually is populated by the very young and the older set. It does have some cool features like the 8 foot wave pool, and Shark Reef where kids can see sharks from the underwater boat or swim with them. TL is very shady generally, especially this time of year...