I lived and worked in the "Grand Strand" (Myrtle Beach) area for a few years. It's a very diverse area as far as vacationing is concerned and rather reasonable price wise. If you are looking for a low key relaxing beach type vacation you can find a reasonable rental house on Pawleys island. Or just north of there is Litchfield Beach which has several beach front hotels/condos if that is more your style. Pawleys island has by far thr least crowded beaches especially if you go to the south end of the island. If you are looking for a hopping nightlife and wanting to go clubbing (not very family friendly and certainly not my idea of a good vaction) you can stay in Myrtle Beach it's self. Between Pawleys/Litchfield and Myrtle Beach is Garden City, Murrells Inlet, and Surfside Beach. All of these towns are probably slightly more affordable than Pawleys/Litchfield but have become so crowded in the last few years that if you try going anywhere you will spend more time sitting in traffic than vacationing and the beaches are far more crowded. As an added benefit, if you are inclined to enjoy a few cold adult beverages it is legal to do so in Pawleys and Litchfield (and certain parts of Murrells inlet but don't ask me where the line is) on the beach as long as you have no glass containers. Conversely if you have small children and would like to have lifeguards while they swim in the ocean you will have to go to myrtle, surfside, or garden city.
Now as far as duck hunting related things to do there is not much of anything in SC. Maybe down south in the Ace Basin area of the state? But there are plenty of natural world related things to do, especially in the pawleys/Litchfield area. Huntington Beach state park has a causeway with viewing platforms and the gators are endless and there is a good chance to see mottled ducks in the marsh this time of year. Across the highway from there is Brook green gardens which offers boat rides in the Waccamaw river to see gators and wood ducks and a variety of other wildlife. To the south is a large bay/estuary area. You can book a fishing charter and do well with the red fish or summer flounder and will be able to see mottled ducks. You may be able to contact some of the large plantations down there as most of them have large duck clubs and they may allow a tour of their property. Also if you like sushi or sea food you'll need to visit Wicked tuna and then have some drinks and listen to the live music (very adult, laid back atmosphere) along the marsh walk in Murrells inlet (only 10 minutes from pawleys/litchfield)