My vote - trailer the boat to Key West, launch the boat and sail to the Marquesses and back. It's about 25-miles each way, incredible waters to cruise, do some snorkeling at Cosgrove Light, snatch some lobsters off the bottom at Boca Grande Key anchorage, and enjoy the beauty of the lower keys. I would tell you to sail to the Dry Torgugas, but that's a fairly long haul over a lot of open ocean for your boat - especially if the weather turns nasty. I know of much larger boats being stuck there for a couple weeks awaiting a weather window to return to Key West. Only 5 miles of open water across Boca Grande Channel between the Marquesses Keys and Boca Grande Key.
A note of caution: At certain times of the year there are lots of bull sharks lurking in the lower keys, some measuring nearly 12-feet. Additionally, the largest concentration of giant barracuda I've ever encountered tends to congregate near Cosgrove Light. Normally, they're not aggressive, but I would not tempt fate by spearfishing in this part of the world. Nothing is more tempting to a barracuda than a fish struggling on the end of a spear and spewing out blood.