I'm not sure how much help I'll be to you. My kids are older, but we do go to Hilton Head. We rent bikes right there from Disney and spend alot of time doing that. I don't know if that will work with the ages of your kids. Can't remember if they have baby seats. They have plain bikes, adult and kids, pedal brakes, no gears. A call to the resort might help let you know if this is an option for you, but biking is such fun around the resort and the island and to the beach house.
We always take a battery operated lantern or two to put on our balcony. There are no outside lights and it is nice to have some light to sit outside and enjoy the evening, especially if the little ones have gone to sleep or if you are eating at the picnic table. Others have suggested also bringing citronella candles to ward off insects.
If you enjoy a glass of wine, you might want to bring a corkscrew, I can't remember if there is one in the unit.
If you are in a one or two bedroom, you should have a dvd player I think, and you can borrow various dvds from the little store on the property, but if there are any favorites your kids like, you might want to bring them.
Bike helmets for the kids if you do the above riding, but you might be able to get those there, ask when you call. We always eat breakfast in the room and usually at least lunch or supper too. I always bring some paper towels so I have plenty. Also round coffee filters and coffee from home and extra sugar or whatever you use. There is a piggly wiggly and a fresh market nearby to get groceries. Let me know if you have any other questions.
