My DS(8) & DD(4) did the Pirate Adventure Cruise from GF when we went down for Marathon Weekend earlier this year. They both had a really good time while my wife and I enjoyed a quiet breakfast at the Grand Floridian Cafe and a stroll around the grounds. Kona at the Poly in within walking distance too and has a great breakfast.
On separate trips over the past two years, my son has done the Albatross Cruise that leaves from the Yacht Club marina and the Jester / Sassagoula River Adventure Cruise that starts at POR. DD was too young to do the cruises on those trips. Of the three, DS rates the Albatross Cruise the highest. The pontoon boat takes them from YC into the World Showcase section of Epcot. If I got the story straight from him, they made stops in China, Mexico, and at the totem poles in Canada searching for clues or pieces of the map. This is before WS is open to the public so there was no risk of them loosing the kids. DS thought it was cool to be in there before everyone else. They ended up eating their lunches on the beach by the Albatross - (In case you didn't know: The Albatross in the name of the ship that crashed on the beach at the YC/BC and was turned into a kiddie pool / crows nest slide - this tour tells the kids the "story" of that ship). We enjoyed a character meal with DD at Cape May while DS (who doesn't like close interaction with characters anyway) was on the cruise. There are many other breakfast options nearby.
In our experience, the cruise from the GF was the toughest reservation to get - tried on several trips unsuccessfully, and ended up having to plan it out to call six-month out from our last trip. If you don't get the GF cruise, don't be let down, a well traveled little boy I know preferred the YC cruise anyway. I don't think you can go wrong either way, it was money well spent. BTW: we've always scheduled this on arrival or non-park days. It is the perfect activity for a rest and relaxation day.