The situation is uncertain. I have no answers, nor does anyone else.
The first question is whether or not you'll be able to get to SXM. The press releases issued by the Sint Maarten government are clear in some spots, and have big holes in others. At present, Sint Maarten is not allowing the entry of passengers who have been in the US or UK in the past 21 days, along with a list of other countries. Scheduled service from the US has been stopped, at least through the end of the month. There are a few repatriation flights coming in to SXM to bring people home, but they end in a few days. What will happen at the end of the month is yet to be seen.
The second question is what you will find should you travel to St Barth. At present, France, including St Barth, is under a lockdown, with restaurants and bars closed (except for takeout and delivery) until April 15. Travel on the island is limited through the end of March, with a Certificate (self-issued) required, and only for limited purposes (for example, grocery shopping and food pickup/delivery). What will happen at the end of the month, and in mid-April, is yet to be seen.
The season's sailing events, the Bucket in March, Les Voiles in April, the West Indies Regatta at the end of April, and La Transat AG2R La Mondiale in April/May have all been cancelled.
There are a number of recent threads here which are worth a read.
https://www.sbhonline.com/forums/showthread.php/98976 SBH Related Coronavirus Information
https://www.sbhonline.com/forums/showthread.php/99026 Cancelling Trip
https://www.sbhonline.com/forums/showthread.php/99006 Flights canceled to SXM
https://www.sbhonline.com/forums/showthread.php/99017 Closure of restaurant bars