L.M.
I can't speak on MO to SC but I can tell you that we recently visited Myrtle Beach and loved it. There is a lot to do...helicopter rides, water parks, beaches, aquarium, and lots more...too much to name. There were some things we didn't do but would have liked to if we had more time and money. Depends on what you like but I will tell you our favorites: Preservation Station at Barefoot Landing (would have liked to have done their tour but couldn't afford that but definately got the pictures done), Ripken Experience, and Helicopter Rides.
I was nice just walking around at Broadway (at South Myrtle Beach) and Barefoot Landing (North MB).