I have cruised to the Marquesas from Key West a number of times -- in a friend's Dovekie, a friend's Shearwater and a MacGregor 26x (very comfortable). No sweat if you watch the weather. In 2000, I sailed my O'Day 23 to the Dry Tortugas from Bahia Honda. Two of us aboard. We stopped by Stock Island to top off our gas, and sailed from there all night to anchor at Fort Jefferson about 1100 the next morning. Beautiful sail. We had a much more exciting trip back. The wind clocked around so it was fair to return, and, although we knew it would continue around to become a norther, we left for Key West. The wind clocked faster than we sailed. It was probably the worst trip I have ever made in a small boat. Winds up to 40 knots, dinghy swamped twice, unable to motor because the prop was out of the water most of the time, etc., etc. We finally made the Marquesas and waited out the weather, having averaged two knots made good for 50 miles. The boat held up fine, we survived, and eventually motored into the prevailing east wind back to Key West after a day of solid rest. We should have waited at Fort Jefferson, but the favorable wind for a return to Key West (a rarity) seduced us into leaving, and then quickly turned very unfavorable. Dumb.
I think the 16 could make the trip in good weather, but it is not particularly fast, and, with that shallow keel, would need to motor all the way home in normal weather, so I too recommend the Marquesas as an easier, safer alternative. That is doable, and good fun.