We love both waterparks, but with that age I pick BB. BB has a well planned & roomy, fun kiddie area especially for the youngest two. Right across the bridge is the Ski Patrol Area designed for the elementary age kids. Lots of activities to do there as well. The wave pool is mild and fun for the younger family, add the lazy river, family raft ride and the great cartoon theme of the park !
I agree with the OPs. We went to BB on July 4 with DS20 mos and DS4 and they had a blast in the toddler area. DS4 also had a good time in the pre-teen area with DH helping him in the deep water. We were with my neice (7) and brother (12) as well. We spent a lot of the day in the wave pool too. Have a great time!