Howdy Adrienne!
I currently have a 7 and 4 year old so while I can't speak from personal experience, I can tell you that I know many others that have children the same ages as yours and everyone has thoroughly enjoyed their time at Walt Disney World and time spent on the Disney Cruises.
When at Saratoga Springs, y'all will not only enjoy time in the theme parks but there are some great pools at Saratoga Springs and you will love being a short boat ride away from the shopping, dining and entertainment at Downtown Disney!
I think one of your best options is to visit the Attraction page on the
Walt Disney World website and the Ships and Activities page on the
Disney Cruise Line website. On both sites, you will find recommended age appropriate activities for everyone in your party. You might turn your web search into a fun family planning session. Have everyone make a list of some of their "must-do" attractions.
We did a land and sea package two years ago and it was one of our favorite Disney vacations! I know you are all going to love your Disney vacation!
Thanks so much for your question and please let me know if you have any further questions as you plan your vacation. Have a magical day!