We just got back from Myrtle Beach and have gone there every summer since I was 11yo. I think it's great for families and really love it now that I have 2 kids. My mom has a condo in the Kingston Plantation so that's where we stay, but I love the location and would stay there anyway. The website is
www.kingstonplantation.com but you can also find rentals through local realtor sites and they might be a bit cheaper. There are a bunch of condos/townhouses/hotel on site, a little waterpark for the kids with 2 slides, a lazy river, and one of those hugebuckets of water that dumps on you. There are tons of regular pools and it's right on the beach (I'm sure mst places are, but you never know). Since there's a hotel on site, there's a restaurant there and a bar and lunch restaurant by the hotel pool/waterpark. Also, they have a kids program with lots of activities all day for them. My kids made tye-dye shirts, got a hair wrap, painted picture frames, and they have lots of other stuff like sand castle contests, pitch burst (where you can break a water balloon on someone's head), dance parties, etc. There's also a sports club on property with tennis courts, raquetball courts, an indoor pool, and of course exercise equipment.
And for activities in the area, there is just a ton of stuff, too much to even mention. There are tons of restaurants of all types, plenty of shops, kid amusements, etc. You're really close to Barefoot Landing, which is basically an outdoor mall/restaurant area, but it has kid stuff too. My daughter did a rock wall, carousel, trampoline jumping on these bungee cords, there's a huge mirror maze, an alligator zoo, and more. And you're not far from Broadway at the Beach, which is another similar type of place but it also has paddle boats and a bunch of rides.