Hello tbtest and welcome to cruise-chat;
congratulations on your decision to try the wonderful world of cruising. You are in for a terrific experience.
To be honest, I'm not all that familiar with Carnival; but a guarantee means you won't get a cabin of a lesser catagory than you bought, and there is the possibility of an upgrade. But I think some inside cabins' beds are not convertible to a queen; I don't think any convert to a king. Hopefully someone with more accurate information will jump in here.
There are many that disagree, but I would urge first-time cruisers to stick with ship sponsored excursions. Get familiar with a port, and then next time (and rest assured, there will be a next time) venture out on your own if you must. If you do decide on ship excursions BOOK NOW! The more popular excursions sell out quickly because so many are booking online now. You don't want to face the chaos at the shore excursion office onboard.
The only port I've been to is Grand Cayman, and quite honestly I can't remember what I did there--must not have made much of an impression. I think it was some kind of historical survey of the island(s).
Well, have fun planning. I've heard lots of good things about Valor. And I'm sure some of our Carnival experts will join in here.
Have a great cruise.