Welcome Aboard, Christina!
You are speaking my language! I am hoping that for our summer cruise I will have everything prepaid, or ready to pay. I will explain that.
So, prior to cruising and booking Port Adventures, your cruise needs to be paid in full, which is awesome for us budgeteers! You can also choose to prepay your gratuities, I believe you will just need to call Disney Cruise Line, unless you booked through a Travel Agent, then you would call them to pay the gratuities. Now for the Port Adventures...
When you book your Port Adventures, you can see the cost. So, I buy Disney gift cards in that amount and then bring them to Guest Services to have them add the gift cards to my onboard account. You can do this for alcoholic beverages and souvenirs as well. You will want to keep ALL of the gift cards until after your cruise, as they will credit back any unused money to the gift cards. Last year, I had a stack of nearly 40 gift cards to go through. I entered each number into the website and found over $50! It was well worth my time.
I have found that alcoholic beverages onboard are extremely reasonable, especially if you stick to the "drink of the day", which is usually something delicious with a special price. You could easily buy a $100 gift card to designate for drinks. Each day, you can visit guest services to see where your onboard account is and how much "credit" you have left.
I will recommend bringing about $20 in singles in order to tip
room service. You should definitely plan to order warm cookies with milk before bed one night! And, we love the "All Hands On Deck" cheese plate. You should plan to tip $1 per item ordered.
I hope this helps you budget for your cruise! Having everything prepaid helps me to completely relax once onboard!
Happy Cruising, Tracy V.