OK, firstly you will have a great time. I would love to go back and one day will I am sure ! We went last year for our honeymoon and had a fantastic time.
This list is what we saw and also some of the things we would have liked to but didn't get round to (but I am sure everyone else will add to this !)
1. Little Tobago Island (& Goat Island if you can) - get Franks tours (based in Blue Waters Inn) and they will take you there, give you a tour of Little Tobago and glass bottom boat there and back, and snorkelling as well.
2. Argyl Falls (we never got to see this - but have heard it is well worth seeing).
3. Take a trip in the rainforest (again we didn't do this but did drive through it a couple of times while we were on the island)
4. See Pigeon Point - if only to say you have been there - it has gone downhill recently I think (my opinion after reading recent reviews), when we were there it was still quite nice - although we were out of season.
5. The Kimmee museum (again we didn't go here but I would have liked to).
6. Take a glass bottomed boat out over Buccoo reef and snorkel. We went with Power, from the Pigeon Point jetty.
7. Definitley hire a car and drive round the island and stop where you fancy. This is the best way to see Tobago - we really enjoyed this. We enjoyed our day at Speyside / Little Tobago and had lunch in Jemma's which is well worth going. As someone else has written a review recently the food was lovely and the only thing we found bizarre was having a menu of fish, shrimp or chicken - nothing at all about how it was cooked or anything ! But lovely food and setting.
8. The Seahorse Inn is a lovely setting for an evening meal - if a little expensive.
9. Sunday School and the goat races at Buccoo.
I think I better shut up now and post this message before my boss notices I am not working !