Not sure what you mean by "total cost including extras." Simply put, soda and alcoholic beverages cost extra onboard just about any cruise ship. There are packages, but you have to consider how much you will be drinking for it to pay for itself. Example, for a can of soda on a specific cruise line, it runs about $2.00 A soda package will cost $6 per day. Therefore, in order to pay for itself, you need to drink 3 cans of soda per day just for the soda package to pay for itself.
Usually what is included in your cruise cost is your stateroom, meals in the main dining room or buffet, and certain entertainment, such as the evening shows, and musicians in the lounges.
Not sure what options you are looking at. I've only cruise by myself, so I can't offer any advice as to 3 people in a stateroom.
If you do a Caribbean cruise from Florida, you will have a total of two days at sea, as it takes a day to get there, and a day to get back. So for a 5 night cruise, you may have two ports of call and two days at sea. There is lots to do on the ship on the days at sea, so you shouldn't get bored, regardless of what line you choose.
As stated, if you are looking at Spring Break, book early. Also, you may find that by booking airfare separately, it is significantly cheaper than going through the cruise line. However, then you may have to consider flying down a day before depending on where you're flying from. My home airport is a hub for an airline, so I've always flown down on a direct flight first thing in the morning, and haven't had any problems.
I hope this helps.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)