Welcome to the world of cruising
Great choice I think carnival is the best cruise line for your starting cruise.
As for the excursions here are my recommendations:
• Always book, specially since you are new to this world, thru Carnival more expensive but you can feel secure since if the tour delays the ship will wait fro you if you do it by yourself there is the risk of losing the ship and they don’t wait for anyone…
• Do one excursion not for the time, for you… I always book only one excursion so I have the time to do some shopping by my own is more relaxing. If you do two excursion most of the time you will be with the stress of losing the other and will spend most of your time like during traffic rush hour.
• Remember the most important rule of cruising HAVE FUN!!!! If you are rush thru it you will not enjoy your cruise and the very first cruise is the best one believe me you will like some time to adapt to this new way of life LOL.