As cash-paying guests, I think you'll receive daily maid service.
As a DVC member, on the 4th day of your stay, they replenish your towels, and remove any trash. On the 7th day, you'd get full maid service.
The bed rails, I'm not sure about. I know when our daughter was 2, we used the pack and play they provide (she was still in a crib at home, so it wasn't an issue for us). Have a terrific vacation!!
You will love Hilton Head! My family had our first visit to the HH resort this past December and I was finally able to convince DH to buy into DVC after the first 24 hours at Hilton Head. Sorry I can't help with the bedrail question.
Since you are a cash paying customer, you will have full housekeeping service everyday. Anyway, I am sure you will love the accommodations and the resort. If you have any other questions about the resort, just ask!