I have a number of thoughts about cruising with older teens. They are all different…how do they feel about dressing up? Most cruise lines are casual, but have one or two nights where you are encouraged to dress up. If they like to dress up, have prom dresses that they have only worn once, a cruise is an opportunity to wear them again. MSC is an Italian line, and though they are sailing from the US, they still have about half of every sailing guests from Europe. My experience is that the European women tend to dress more smartly in the evenings than we are accustomed. The more international flavor might be interesting for the teens. So, since you will be driving to the port, the amount of luggage will not be a concern.
My second thought involves cabins. You have teen girls. One bathroom per cabin, and they are not sized for two at a time. Sailing from Port Canaveral, carnival Magic and Mardi Gras have ocean view cabins (deluxe OV) that have a split bath. One has toilet, sink, shower, the other has sink and small tub. That second sink and mirror might be a peace saver…. EM