We took my 4 year old to Typhoon Lagoon last year on our last day. He loved it and named it as his favorite park. They have a smallish slide that he loved and that you can stand at the bottom and catch him. There was also an area where he could shoot water guns at other kids. I think it was a boat. All the kids were having a great time. They have family raft rides that are great too. I'm not sure if they have life jackets.
I've never been to Blizzard Beach so I can't speak for it.