Welcome aboard, Martha! No matter when want to set sail, you can count on the fact that Disney will have many stateroom choices, sail dates, and four magical ships so you can put together the itinerary that is best for your family's budget.
Since the currently released itineraries only show us the sailings through December of 2015, you won't be able to book or get exact details for a summer of 2016 sailing just yet. I'd expect to see those dates released early next year. But, the current prices and options will give you an idea of what to expect. It looks like you'll need two staterooms for your family of six, so check out the adjoining staterooms so you can have a door between your two rooms.
When you book a cruise with Disney, you'll put down a deposit and after that, you can pay however much and however often you'd like, as long as your cruise is paid in full by 75 days prior to setting sail. So, you can make your own payment plan that works best for your budget!
Now, since you don't have an exact cruise to book just yet, if you would like to go ahead and start saving, there is a fabulous new program through Disney that allows you to save for any type of Disney vacation that you might be interested in! Check out the
Disney Vacation Account. This new program allows guests to start saving up to five years in advance and apply their funds toward a Disney vacation, including a cruise. There are tools that allow you to estimate your budget, create your savings plan, and track your progress. I love the progress tracker because I'm a very visual person. It's great to be able to see how much I've saved and how much more I'll need before we set sail!
Once the itineraries for summer 2016 are released, I recommend you book your cruise as soon as possible, as the best prices will be available and you'll get a better choice of staterooms. Have fun, Martha!