The dogs are often busy. Personally, I wouldn't take up a mooring ball there for that amount of time.

Why not have them pick you up at Scrub or Marina Cay? Boat can be on a dock where you wouldn't have to worry about moving it for any reason and you can use the dinghy to go over to diamond reef to snorkel. And this way you aren't taking up a mooring for an extended amount of time.