We just got back yesterday from an all waterparks trip. My DS is now 8, and we just loved TL. (It was beautiful, shady, etc.) That said, when he was smaller, we loved BB. Yes, there are some wild slides at BB. (He still is not interested in Summit Plummet or Slush Gusher.) But there are two kids areas at BB (Tike's Peak for little ones and Ski Patrol Training Camp for the slightly more adventurous). After just being in the surf pool at TL, I can tell you that I would not take a little one in that wave pool. The surf waves are HUGE. So, the wave pool at BB is more appropriate for children your kids' ages, too. The lazy river is about the same at both parks. So, I think BB is probably better for kids 3-5.
Hope that helps!
Julie