I've been to Typhoon Lagoon, and don't recall them having much of a children's area, though at the time I didn't have children, so I wasn't really looking.
I've never been to Blizzard Beach, but I vaguely remember reading about a children's area. Tyke's Peak? Or am I making that up???
Anyway, I am also taking a 2-year-old next summer, and was planning on going to Blizzard Beach.
The only other thing to consider is that Typhoon Lagoon is shadier. Blizzard Beach I would think would be really hot with the sun reflecting off all the white "snow". So make sure to pack waterproof sunscreen if you go to Blizzard.
Hope that helps!