ok. kere goes.....
assuming your g/f doesnt know about the trip?:
*you "kidnap" her, for want of a better word. pack her bags for her, keeping in mind what she would need for the trip.( Be sure to get help from a female friend of yours or hers - you need the mind of a woman to make this work

) blind fold her at home, put her in the car and take it off only when you've arrived @ the airport. By this time, she should figure out what's goin on....
n.b:- DO NOT forget her passport!
* when you get to Tobago, you are driven to your hotel, rest for a bit , change clothes, then take her for a picnic. my b/f suggests you rent/hire a boat and picnic on No Man's Island (an uninhabited island off Tobago. remember to carry water, as there's no natural source there)
Anita once suggested to me a picnic & snorkeling at Arnos Vale in reply 2 my snokeling post, so you have 2 choices here...
*In the evening, you take her to a classy restaurant for dinner. have an exotic meal w/ choice wine, ect... Here's where you give her a nice gift - flowers will do

(doesn't have to be expensive or extravagant, as i'm sure you would have covered this territory with the trip and all

)
*now you take her to one of the clubs and dance the night away.....
Be
sure to take pictures at every phase, even before you leave home. i say this because these pics can come in very handy (you can put together an album of your times together and this can be part of another gift later on...your anniversary or s/thing.

)
perhaps one of the other forum members can suggest a particular restaurant and club - or you can read the reviews and decide where you want to go
--Let me know how it goes,ok?
Best of luck, Carla