Your DS will LOVE the cruise, you really should let him go... and make those reservations quickly... they go extremely FAST!!!
DD went when she was 6 and loved it! The cruise starts at the GF marina, and you have to arrive 15 minutes prior to scheduled time so the kiddies can be fitted with proper life vests, get their pirate gear, and you can sign the papers, and pay.
From the GF, they sail to the beaches of the Polynesian, the Contemporary, and the Wilderness Lodge looking for pieces of their pirate map. Once they have assembled the pirate map, they sail to the beach by River Country to dig for treasure. The treasure actually consists of mainly pirate style party favors. After they dig, they get back on the boat, and sail for GF. During this time they do have a snack of juice, and in my DD's case, grapes. The booty is divided evenly among the kids when they return. You must keep your receipt that you were given prior to the cruise to claim your kid at the end.
There are 4 adults who work with the Child/Life department who go on the cruise... usually, it is 3 or 4 kids per adult. 2 of the adults are certified lifeguards. I felt very save with my DD going with them.
Hope your DS has a great time!