To get to Bequia, the second largest island in the Grenadines, connecting flights from Toronto to St-Vincent are available during high season; then a ferry will bring you to the island; or you can take an international flight to Barbados, then a short inter-Caribbean flight to Bequia.
Temperatures are pleasant all year round in Bequia; ideally, avoid periods from May, it is the rainy season; from the end of June, the hurricane season. So from January to April, it is the dry season and the best time of the year to go there.