I understand that each person is allowed to bring a limited amount of soda with them. Silly question, I assume they allow coolers? How large and considering luggage how does one manage everything during boarding? As you can tell this is our first cruise. Thanks!
On Carnival the maximum size for a cooler is 12"x12"x12". They are usually pretty strict with this also (should be within an inch or two).
I personally have used the cooler pictured below on a Carnival cruise before. It's made by Coleman and the actual dimensions are: 12.37"L x 10.13"W x 13"H. It's soft sided but includes a hard plastic insert if you want to use it.
...as for carrying everything. A rolling suitcase and this cooler over my shoulder is all I would need. As a first time cruiser you are going to overpack by ALOT! I think most first time cruisers pack double (if not more) what they are actually going to need / use, so keep that in mind. Here are some good suggestions on what to pack / bring on your cruise: Carnival - Pre-Cruise Checklist.
I would not recommend putting it in your checked baggage, but it is not illegal.
Checked baggage on most aircraft is heated or pressurized (although on some smaller planes this will not be true). The main concern would be rough baggage handling. The last thing you want to worry about is having to do laundry when you should be enjoying the sailaway party sipping a cocktail of the top deck.
We bring a collapsible rolling cooler. we pack it in our bags. Great for storing unopened buckets of beer, wine allowed on, water, etc. Give the room steward a tip and he will make sure the cooler is always iced.
Another point to remember. If buying soda card, wait till the ship is in international waters (away from dock and out typically 3-10 miles) and you save the sales tax charged.