Having just done 6 days in a cabin last month, I would vote for a cabin rental over a camper. Think about it. You will be just coming off a crowded cruise ship, where you have been surrounded by lots of families and tourists, and huddled into a shipboard cabin with 3 growing boys. A cruise can be very relaxing, but they are not without the herds of people as you line up for muster, meals, excursions, embarkation, and debarkation.
Do you really want to go from one cramped quarters to another? The cabins are serene, and much more roomy then a camper would be. You would have a full kitchen, dishwasher, full size fridge, and a separate bedroom where you could store the boys, so mom and dad can have the solitude of the murphy bed in the living room. It was quite comfy for DH and I. We used the deck as an extension of the cabin, and found that it gave us a camping-like experience, without as much work. There is a grill right off the deck, where you can cook out to save some $$$$ on meals. Either way, you will still have to go find groceries to stock the camper or the cabin. The cabin boasts a pantry and all the cooking, and eating utensils, you could need, with the exception of grilling tools. Luckily, I had read about this lacking feature here on the DIS, and packed my own grill tools. And lets not forget you will have a full size bathroom with a tub and a shower head! (and clean towels, and and mickey shampoo, and mickey conditioner, and mickey lotion......lol)
One of the biggest benefit of the cabins is Mousekeeping, who will even do your dishes for you, and clean the grill. You won't find that in a camper rental.
After doing the parks, we loved coming back to the relative serenity of Ft. Wilderness, and liked the seclusion the cabins offered. After being around lots of people all day long, I welcomed our little cabin in the woods. We were a party of 4 adults, and 1 child, and it worked out wonderfully for us. But I understand, every family is different, and preferences will vary.
Having done a cruise before, I am pretty sure I would not have the energy following a cruise, to then set up camp, with cleaning, unpacking, stocking, etc, and then have to do the opposite at the end of the rental period. You will already be tired from the cruise, and then even more tired from your time in the parks. Camping is a lot of work. If you can afford it, go for the cabins. You can always try the camper next time. Just my two cents.