I've been on quite a few cruises. I would not pay for an upgrade to a ocean view room ever. The windows are small(er) and do not provide you any real view. To me, it's a waste of money. (Besides, a balcony is usually not much more.)
That being said, I don't even highly recommend balcony rooms for caribbean trips because all you see is water.
Now, in Alaska I would recommend a balcony because you can sight see right from your balcony as you go through the inside passage. But in the caribbean, its just vast expanses of water and I don't understand why people pay the large premium.
Inside room is almost always a much better bang for your buck and you can sometimes (I said sometimes!) take an extra cruise for the savings from booking an inside room over a balcony.
(Case in point- my wife and I are taking a 7 day Eastern Carib. cruise in August on the Carnival Liberty. We paid $1000 total after TT&L for an inside room on the Upper Deck. The upgrade to a balcony would've cost us another $250pp. For that extra $500, we could've almost paid for an inside room on a 4-5 day cruise out of Galveston on the Ecstasy, which were around $800 total at the time.)
On your original question- they will push the beds together and it will be just fine. If you booked through a travel agent, ask them to request it. If not, you could always contact a Carnival Cruise Rep (check Carnival.com) and give them your reservation # and have them make the change for you. Even if its not done right when you get there, request it and your room steward will have it done for you.
I also second what everyone has said about the food. I don't know if I'd compare the food to a 5-star luxury restaurant (although some specific dishes from the dining room may be close), but it's all very good and there is a huge variety. There is no additional charge for extra food, so do not be afraid to try things out and order something else if you don't like your first choice.
You will have a blast.