Kat - Most of your questions have been answered. I'll add a little more. The water on the ship is very drinkable - actually better than some bottled water I've tried. There will be a liter-sized bottle in the cabin, for which you'll be charged $3.75 on your S&S account. Also - remind your daughter that the Cokes/Sprites in the cabin are NOT complimentary - $2.50 each. And yes, your best bet would be to take your own soft drinks - Carnival allows a 'reasonable amount' to be brought on board at embarkation.
Also a coupla bottles of wine. Hard liquor and beer are not allowed, and will be confiscated if found.
There are a lot of beverage choices at no charge. On Lido Deck, there are self-serve machines with various juices, lemonade, and fruitpunch, coffee, decaf, iced or hot tea - all day. At breakfast, also hot chocolate, chocolate milk, and regular milk. From room service (no charge for any food or beverages except for alcoholic beverages), there's also a good variety. As Serene said, tip the delivery person $1 or $2 each time.
Your first cruise - SUCH fun! I bet it won't be your last!
**Edited to add:
Duty-free means NO tax.
Basically everything on the ship will be charged to your Sail & Sign account. Very little cash is needed on the ship. Anything you purchase (souveniers, photos, alcoholic or soft drinks) will be charged to your account. The first thing you'll notice on your account is the $10 per person, per day automatic gratiutities....this covers:
$3.50 per person per day to your cabin steward
$5.50 per person per day to your dining room waiter & assistant
$1.00 per person per day to the Lido Deck dining personnel
***Edited again (sorry) to say:
If you go to the art auctions, you'll receive complimentary champagne. And don't miss the Captain's Welcome Aboard Party, which everyone is invited to. LOTS of comp drinks of every kind and hot and cold hors d'oeuvres!