Hi Cameron!
Thanks for your question and for visiting the Disney Parks Moms Panel!
Both
Typhoon Lagoon and
Blizzard Beach are immensely popular year round, but especially so during the hot, Florida summer months. I would expect to see heavy crowds when you go.
The good news is that both water parks are large with many attractions at both to spread guests around.
One suggestion I have is that IF you are planning to take a break from touring the theme parks and spend a day at either water park, get there as soon as the park opens.
Disney bus transportation runs from all
Walt Disney World resorts directly to both Typhoon Lagoon AND Blizzard Beach.
Also, if you need to rest tired legs with a day of relaxation and are not up for the crowds of a water park, I would simply hang out at the resort pool for the morning and maybe head to the water parks late in the day as crowds thin out a bit. Either way, you are sure to have a Splash-tastic time!
I hope this helps and I wish you a Magical trip!!
Chris