We did BB in Jan. with our kids and have a 4yo.
(Typhoon Lagoon was closed so we didn't get to go to make a comparison.)
While there was definately more for my older kids to do, my 4yo had enough and had a really good time. We did Teamboat Springs as a family several times and everyone loved it. The chairlift ride was like a ride for DD4 in itself.
She had fun on it. We also did Tike's Peak which was perfect for her because she could do most of the activities independently while we watched her.
We did the wave pool and she also loved some of the slides at the Ski Patrol Training Camp, the area for older kids. There was a slide there that she went down probably 25 times while my older ones did the activities there. I stayed at the bottom in the water and caught her...it was no problem to do that.
While the older kids did some things for only them with my DH, I took her for a snack and a little shopping. It was a fun day and felt while there could have been a little more for her, it was adequate. It wasn't hot, 70 degrees, so we didn't feel the need to be in the water all day. It was the first time we've gone to BB and I would love to try TL, but would definately do BB again.