Definitely an ambitious plan - shame to be missing all the attractions along the way. Especially Charleston, Nevis - a very charming spot (anchor off Pinney's Beach). Pretty much your whole trek from St Martin to Antigua will likely be upwind.
Your day three will no doubt be the toughest, how tough depends on whether the trades are in their NE phase or SE phase - We lucked out and had a dead spinnaker run from Jolly Harbour to Charleston a couple of years back, and then had the trades swing SE for a reach from Saba to Simpsons Lagoon St Maarten.
The beat from Nevis to Antigua might be punishing, especially that "early" in the season.