I'm no expert but we've vacationed there a few times. If you're looking at North Myrtle try http://www.condolux.net. You can get a 1 bedroom condo with a kitchen for roughly the same price as a night in a hotel and most of the condos have an indoor pool along with the outdoor pools.
Dunes Village has 2 indoor water areas. Captains Quarter's isn't as deluxe but they have an indoor pool, lazy river, and hot tub as well one round of free bowling a night at onsite bowling alley-ask for updated room very budget.