Hi there, Andrew!
Of the two water parks on Disney property, I would recommend
Typhoon Lagoon without hesitation for the ages of the children in your travel party.
Blizzard Beach is just full of action-packed slides, and does require quite a bit of climbing up the "mountain" to access the fun. Typhoon Lagoon, on the other hand, offers a wealth of activities and areas just right for the younger set that might not quite be ready for the higher altitudes.
After trying out some of the body slides and family slides, your travel party can enjoy Castaway Creek, the 2,100 foot lazy river.
And Ketchakiddee Creek is the perfect toddler/youth water spot, featuring scaled-down slides, waterfalls, water jets, and much more.
Have a wonderful time!
See you later, celebrator,
-Deborah B.