after driving about 30 years on the right side only this year in May I visited Tobago - worrying also about driving on the left.
And.... no problem. And also I didn´t made the experience that the Tobagonians drive in the middle (well, a few did
But if you don´t drive in an aggressive way and concentrate a bit then ther really should be no problem. I recommend to use an automatic car - so you can forget about shifting the lever with your left hand.
Additional now is no high season. So there will ne not so much traffic.
Enjoy your stay and I wish you not to catch too much rain.
Best regards and happy cruising by car