I use Google Earth
as a planning tool. Using this, your straight line distance will be 100-110 nautical miles, depending where in Grenadines you are wanting to go. It should be a broad reach.
Use Google Earth
to get images
of the route
and your destination
, and it will help you visualize the trip.
The time sailing will depend on your boat
speed, but, for example 22 hours at 5 knots. Definitely an overnight trip for most boats.