Jesse Jones-Armour
Google
Disclaimer, I'm not sure how to rate an entire island, also I love Tobago so I might be a little bit biased.
Tobago is a lovely place on a whole to just chill and relax, with its laid back atmosphere, and plenty outdoor activities and festivals.
It's (fairly) easily accessible from Trinidad by ferry and plane. I do recommend to bring foodstuff with you though, as everything is considerably more expensive than Trinidad.