Going alone on a Disney Cruise with a five year old?

I really want to do this with my son, being a single mom I am use to doing things alone with him. But this is a huge step going on a cruise... I am really nervous!! We are driving to NYC because I live close to port about five hours if that away. Than we will be on a 8 day cruise to Bahamas, castaway cay and a day at Disney world included in the cruise. I know it will be fun but I am scared to be alone, I offered to pay my baby sitters way but she can't go. So I figured at least if it is just him and I we can do what we want with out having to worry about what some one else wants to do. Has any other single parents cruised alone before any words of encouragement??