I would have to agree with most of the advise on here except to not bring the baby sitter and use the daycare / nanny / sitter that the resort offers. I can't see leaving your kid with some stranger (yes I know the word stranger was already debated, no need to go there again) especially when you are more then capable of paying your personal sitter. Would something happen to your kid in the care of resort staff? Probaly not, but if it did would you be able to live with yourself knowing you were just being cheap and not bringing your sitter? I know I wouldn't. On the other hand I cant even afford a vacation let alone bring another person with airfare, room, food & pay. Hell, I dont even really go out with my wife alone cause I cant even afford a sitter. Then again I love being with my kids and take them wherever I go and we always have fun. If its between diving and having someone strange watch my kids, looks like im not diving. When they are old enough to dive we wont have any problems!
Bring the babysitter, I am sure you wont regret it and pay her a flat wage for the week plus room, food, airfare and work out a schedule that she will need to be flexible with.