Hi Lori!
All the restaurants at Typhoon Lagoon and Blizzard Beach are quick service restaurants, and yes, you certainly can use your Dining Plan at either.
At Typhoon Lagoon, the quick service places are: Leaning Palms and Typhoon Tilly's.
At Blizzard Beach, the quick service places are: Avalunch, Lottawatta Lodge, and the Warming Hut.
At both parks, there are generally outside carts that serve snacks and beverages, but check with them first to see if they honor the Dining Plan. some cart vendors are third party, and don't honor Disney dining.
Other than that, you should be good!
Have a magical SPLASH on your visit!