You may want to look into the Boardwalk Inn at Wild Dunes Resort on Isle of Palm.

The actually geography of the beaches in Kiawah, Wild Dunes (IOP), Sullivan's Island, and Folly Beach are pretty identical.

I like Sullivan's because it has a more 'local' feel to it and you are only 20 minutes from downtown.

The big point here is WHEN do you want to visit? No condo will rent to you for two nights in June, July, or August or over major holidays.

There is a hotel at Wild Dunes that may not have minimums.