I would book a night at the Sonesta Maho, take taxi over, check in, either chill at the pool or beach right there or walk to Mullet for the afternoon. Then your trip to the airport is under 5 minutes and an 8.00 cab ride. You won't have a chance for any traffic. If your flight is at 2:00 on a Monday, I would get there at 12:30, which gives you the morning, get up early, grab breakfast at Sunset, watch some planes, walk back clean up and head to the airport - thats what I would do!