We have several hotels advertising with us... all of them are good choices... but I think Chateau, Edgewater, Boardwalk and Beach Tower stand out as family hotels:
Panama City Beach Hotels & Resorts

Also, check out Sandpiper Beacon... I haven't been inside any of their rooms in quite a while, but they have an indoor water park and mini golf for kids:
Panama City Beach Hotels - Florida Family Vacations - Spring Break in Panama City Beach Florida

Splash Resort also has an indoor water park:
Splash Resort Condominiums - Panama City Beach, Florida

Good luck and welcome to the boards!