you should have no problem going from your hotel directly to the pier.
Wait until noon to check-out, by the time you are all checked-out, get your kids and luggage in order in the lobby, find a cab and get to the pier, get to the pier, get unloaded, well you get the idea, you should be able to check-in and board.
We just got home from the Destiny on Sunday. We checked out of our hotel at 11am and went directly to the pier. We too had VIP check in. We were there before 11:30am, gave our luggage to the porters, walked in, were directed to the Skippers Lounge and were checked in in a few minute. We were on the boat by 1:000pm. Very painless.