Hi Wendy,
Very excited for you!! There are two 24-hour self service drink stations on the Disney Dream. These stations will offer a selection of fountain soda, iced tea, milk, tea, coffee, hot chocolate etc. Filtered water is also available here - it is from the soda fountain machine, not bottled.
I prefer to purchase a bottled water package. I like having the bottled water available in our stateroom, and it's nice to have for taking on excursions. We always pre-purchase a
water package and appreciate the convenience of having it delivered directly to our stateroom. If you don't pre-purchase, there will be several opportunities to purchase the packages upon embarkation, and the water will be delivered to your stateroom later that day.
I hope this helps, have a great time!