Sorry--I was assuming you were looking at the Disney brochures with the multiple excursions that have Stingray City in the name. I have done it with Don Fosters--but I know that in the past, they weren't interested in doing cruise ships. I believe they tend to do their stuff way too early before the ships anchor.
Having said that, I have done excursions on my own on prior cruises and know you can save a bunch of money. Just be sure to understand refund issues if for some odd reason we can't tender in--yes it has been delayed in the past due to high waves. Also, I called to the company from the island prior to the stop and checked in.
Good Luck
DG