Man this is an old post. I've kited in CB quite a few times since then. It's actually not that hard to find a launch site on the Bras'dor Lakes. There are (or was) a few kiters down near Port Hawksbury. Also had a great ocean session at a beach close to Louisbourg. I haven't been there for a number of years though. The last few times we went down we went to PEI and got my parents to drive there, from CB, to meet us. There is a pretty vibrant kite scene in PEI and great riding in warm water. Where CB you will be riding by yourself (unless you are with someone) and the ocean temps are a lot colder.
I can confirm that there is a great kiteboarding scene on PEI. My inlaws live there so it's generally not too difficult to make the case for a PEI weekend trip, then I spend most of the weekend on the water. Kite Point
in the northern part of Malpeque Bay is simply awesome with lots of shallows and relatively flat water. For the past couple of years the PEI Kiteboarding
folks held the PEI Kiteboarding Throwdown at Kite Point. Has a nice grassy launch/landing area.
There's plenty of other kiteboarding spots on the island