I have a 4yo and 2.5yo and have not taken them...BUT...here's my assessments---
Typhoon Lagoon -- snorkeling w/sharks (probably not

~)
wave pool -- only in the front because the waves get BIG
lazy river -- yeah
family style slides - yeah
little kid area - yeah
other slides - too young
Blizzard Beach --
kids area - yeah
all types of slides-maybe some
lazy river - yeah
pool - yeah w/mom or dad
I think in my 2 cents worth that there is more for the younger set at BB, but personally I LOVE TL. For the kids though...BB is my idea of a safer bet and more for the kids to see. My ultimate pick would be RC, but they closed my beautiful RC down! I have pictures of me there at very young ages and remember riding the slides/swings. I suppose it all depends on the child's swimming ability and who is going with them on the slides and such. TL has the best wave pool, but like I said it is made for body surfing and in the middle it can lift a full grown adult WAY UP in the waves and crash you down. Haven't been to Aquatica yet, so couldn't tell you there. HTH you some


PS
If you are at BB, you are right next to the minigolf courses too. It gives you another thingto do, if the water parks doesn't pan out or if you have to leave early for lack of interest