I run one of the dive shops in Carriacou and have logged up 1,000+ dives there in the last few years. If you love wrecks and walls, then this is not the place for you. But of you like vibrant. colourful reefs, with lots of drifting in gentle current (maybe not so gentle in February) in the Grenadines, then Carriacou will probably tick many boxes. The island has three reef based sites which I would suggest are amongst the best sites available on a consistent basis in the Eastern Caribbean (one of them I would dive every day if I could). The island is small and welcoming, with tourism not really an industry. People arriving on the island are not hassled or harrased, and you even get change from the waitress at the restaurant. There are parties on the beach most weeks, and at 7 miles long you can be pretty much anywhere in a few minutes.
February 16th is CARNIVAL too - so this will be a busy week of parties and mas (the Shakespere mas and juivert are really worth seeing). The weather is usually dry and warm, with cooling trade winds keeping a lid on things. The sea can get a little bumpy, but nothing that a good dive catamaran can't handle!
Travel options to the smaller islands is a little more tricky, and we're suggesting if you can not get direct into Grenada (SVG puddle jumper from Grenada is an 8 seater, and if you can't have your luggage with you it comes on the next flight - does not happen often though) then fly Barbados and Union Island. Here the SVG plane is a little larger (20 seats I think) and we organise coming to Union to pick you up on one of our dive boats and drop you back at the end of your stay - all part of the service!
If you want any more information, pm me through Scubaboard or check me out at Deefer Diving