Blizzard Beach is kinda cartoonish so the kids love it.
The very young kiddie area is big, well planned, off the main track and looks like alot of fun. Lots of parent seating and lifeguards highly visible.
(Typhoon Lagoon's was originally very small and right on a main path. My 3 year old was bored and I didn't feel the location was well planned. It has since been expanded by I found it to be alittle crowded and chaotic.)
Back to BB, right across a bridge from kiddie area is the elementary age play area which my younger one loved. Your older one (and maybe younger one) should be able to do enough there too. Floating ice, small raft slides, zip slide.....
Of course they can do the lazy river and hopefully family raft. The wave pool is much calmer than Typhoon Lagoon and enjoyable for young ones.
Kids area are both to the right when you go in the park.