Ro, First of all- Yeah! You'll love cruising. I will try to help as much as I can, been on two previous carnival cruises.
1- You will need cash for the ports and best for ship credit is a credit card. There are other options for the ship credit-but I am not familiar- we set up an account at a separate bank- its our cruise account- we use the atm/debit/credit card for the ship credit. Works perfect- daily limits do not apply at our bank- all is charged at once at end of cruise- as long as you have that amount in the bank- it works fine.
2-Formal night there will be tuxes but not all. A suit is fine. He sould wear at least dress pants, dress shirt with a tie. Dress shorts and a nice polo shirt will work for other nights.
3-Dress comfortable and casual most of the time. You will see t-shirts and shorts, sundresses, and so on. 1st night is no different than last on formality.
4- Cell phones didnt work much for us and VERY expensive to call home from ship.
walkie talkies didnt work well- too much use by others, you get mixed up.
5-bars as well as Anything on ship- charge to ship room credit. No cash on board except maybe some tips.
6- cozumel was fun, nice and safe. In any port, just be aware and stay together- always with someone at night.
7- Valubles should be fairly safe- our room safe malfunctioned with jewlery and cash inside and our room steward had to get his manager- and then He had to get His manager to open the safe- only a few people on the ship know how to do that. keep inventory of what is in there at all times.
Ro, best of luck, enjoy!
P.S.- some tips:
Pack suitcases half yours/half spouses- this way if one gets misplaced- you each have some stuff. Pack a carry-on for the ship with bathing suit and change of clothes, luggage may not arrive until late.
Get to the port early- we were told we couldnt board until 12:30= we were there before 11 and on the ship at 11:18am!!
Let us know how it goes!