If you like the beach and to be entertained, on the east coast, Myrtle Beach SC, would be a good fit for you, there's nice beaches and so much to do for a family, something for everyone. Golf, shows, restaurants, shopping, mini-golf, attractions, water parks, etc.
If you like to throw in history, you can combine the trip with Charleston, SC.
They have beaches there too, lots of great dining and shopping and lots of history among southern charm.
If you keep heading south, you have Hilton Head Island and Savannah, Ga.
Hilton Head has wonderful beaches, but is more quiet with things to do unless you love golf, riding bikes, fishing. It's more of a down time destination, but then Savannah is a short drive away for some more history, shopping and restaurants.
ETA: The Outer Banks is awesome, and yes, there's quite a bit to do there to, but more active stuff rather than "entertainment" like Myrtle Beach would be. It's a true destination spot. Once you're there, you want to stay put and do things locally.
It's funny though, because we've done all that a lot, so I'm ready for a change, and Cannon Beach in OR sounds heavenly to me!