The previous advice should be helpful and worthy of being followed.
I know I have a different point-of-view than the above by stating that later boarding is not really a huge problem, especially since you usually drag a bag of stuff with you (check everything you do not need access to prior to 5pm, when most of the luggage is delivered outside your room) until the rooms are accessible (1:30 pm or so). By being in a later boarding group (I think we were group 42 in recent Cape Canaveral/Fantasy cruise), you avoid some of the impatient crowds especially at the pre-board photo. Also, since it seems you have at least one youngster (your photo), they can see characters in the terminal, view the ship model, and you all can review the Navigator (plan your day) while waiting for your group to be called. Once on board, you can do the lunch (Cabanas/Topsider) and then hit the pools/aquaduck. Bottom line, not the end of the world to not be first aboard. IMHO, cruise starts after we unpack in our cabin, then the fun begins.