hey Charlie..
I live in NS but I've only been down to Lunenberg to dive a few times. There is an artificial reef... the former HMCS Saguenay, that is an interesting dive.
Seal rock is a blast, we got some fantastic pictures.... If you lie on your back and wiggle your fins the seal pups will actually come up and tug on your fin tips.... it was fantastic! The bigger seals don't come too close, but the pups will come right up to you.
Those are the only 2 areas I've hit down that way. The shop that used to operate in Lunenberg is now closed, so there's no fill station nearby. The closest I know of are in Yarmouth and Halifax, there may be something closer, but I am not aware of any.
I can recommend one charter operator from personal experience...Capt. Bill Flower of Lunenberg Ocean Adventures, (902) 634-4833.
Something else you may consider is shark cage diving. Bill has a cage, he takes you offshore about 20 km or so, and drops the cage in the water. After some chumming, some sharkys come sniffing about, and in the cage you go. They've had up to 12 Blue sharks in one sitting, but average is more like 3 or 4. My wife sent a story on it to Diver Magazine, the article and pics are in the March issue. It's a Canadian mag, so I don't know if you guys have it.
I hope this helps a bit, if you have any questions, feel free to PM me. I hope you have a great trip...
chris