We didn't book ahead for CC, but I suppose it might depend what you want to do. The floats, bikes, boat rentals, etc. can be done on the spot (for boats you might need to check first thing in the morning to see what time is available). Excursions like the stingrays are popular and might get booked up - in fact, if you are sailing "in a couple weeks" many people may have signed up as much as 4 months ago when their booking window opened so there may not be availability. If it's a lousy weather day and you decide to remain on the ship, you would be charged for any excursion you pre-booked if the ship does in fact dock, so it might be wise to wait unless there is something that you absolutely don't want to miss.
Enjoy your cruise!