Karmen:
I get this question often because we've had Water Park Annual Passes in the past.
Although you might find one or two dissenters on the Mom's Panel, I think you'll find that many of us feel that
Blizzard Beach is more appropriate for the younger set.
Its Tike's Peak area seems better-defined to me than Typhoon Lagoon's, and I don't have to run through foliage (like what you'll find at TL) to locate my child on its slides. Several picnic tables and LOTS of chairs are in the area, too, that's off the beaten path from the other slides and attractions. You might find that your 3-year-old can even "graduate" to the longer slides in the pre-teen area after he feels comfortable (they have lifevests, too, at Ski Patrol Camp).
If you have an active boy, he'll enjoy the ski lift up to the family raft ride (which is longer, by the way, than TL's which can only be accessed by foot--up stairs). The wave pool was more appropriate for our little guy than the tidal pool at Typhoon Lagoon, too, which found me with my head below water several times.
Don't get me wrong, if my only choice was Typhoon Lagoon with my toddler, it would still be better than most any other water park we've visited. But Blizzard Beach just offers more, in my opinion, for toddlers.
Wishing y'all a magical vacation!
Whitney