Hi, Nicole!
Having been in that predicament before, I will recommend - unreservedly -
Typhoon Lagoon as the better option.
Blizzard Beach is definitely more for the tween-and-up Guests. The theme of the ride - a ski slope - makes negotiating the paths to and from rides rather lengthy (lots of uphill for little legs!), and that water Park relies heavily on body slides and fast-moving plunges.
Typhoon Lagoon, on the other hand, has a reasonable amount of climbing per ride; do bear in mind that the tubes for the single-rider tube rides are not "sized down" for children, so you might need to plan on carrying smaller riders' tubes as well as your own. They can get bulky.
There's a lovely children's play area, family-friendly lazy river, and many more slower-paced body slides and family rides than at Blizzard Beach.
And 48" is just the height when riders can experience the awesome
Crush'n'Gusher, a fun water-coaster that can accommodate three riders on a "raft."
Either way, you're sure to have a wet, wild time - and don't forget the sunscreen!
See you later, celebrator,
-Deborah B.