I'll try and throw some of my input on a few of these questions.
2. Greg Norman's. I haven't been there but the rest of my family has and they love it. It's in the Barefoot Landing area.
3. Boardwalk Billys. If you go during happy hour they have specials...I beleive last year I paid $5 for a half pound of crab legs
http://boardwalkbillys.com/?page_id=6 that's their web site.
5. Crab Catchers (Little River) The Shack (Cherry Grove) Quigleys (Murrels Inlet)
8. When I was your kids age I enjoyed going to Dick's Last Resort. Food is okay, prices may be high, its a one of a kind venue. If you want a cafeteria type experience hit up K&W at one of their locations. Both are american restaurants though
9. Liberty Steakhouse in Broadway at the Beach. I advise you don't have a meal there though, their service has gone down hill fast and may have hit rock bottom. Decent micro brew though. Also check out New South Brewing, I may go there this year.
12, 13 & 14. There are quite a few, I'm sure you'll see ads for them everywhere. Grab one of the coupon books as well.
15. Charleston SC, Calabash, Myrtle Beach State Park.
17. Myrtle Beach has the Boardwalk (I dont think it's that great) and it has a ton of restaurants, but nothing you can't really find in the NMB area. Broadway at the Beach is a must as well as Barefoot Landing for your daugthers. Might want to check out Pepper Palace, Margaritaville (if you're into the touristy stuff), Cheeserburger in Paradise, plus all the attractions BATB has.