Most of the charter boats in the BVI I have sailed don't provide much flexibility in your response. Mainsail reefs often aren't rigged. As Bill said, in that situation the best you can do is drop *and stow* the main. Tie it down, zip the sail bag, whatever. Even with the zipper type sail bag you would be well served to throw a couple of sail ties around the whole thing. Roll up some of the jib (at least to the first reef mark, perhaps the second).
Most charter trips have plenty of people. Make it someones job to walk the deck edge and check for lines over the side before starting the engine.
On my boat I triple reef the main, roll up the jib, and hoist the staysail. When a squall comes on me by surprise I do that anyway, I just get wet. I'm odd though, so YMMV.