Your best best is likely to get ahold of Brad (Burness a few posts up), he seems to be most in the know.
I was just there for two weeks and in the Gander area as well, unfortunately I didn't find much in the way of kiting right in the area, realistically you need to commit to a drive. I'm sure that would be different if I had another kiter with me, there had to be spots around the loop (Gander around through Gambo) but I'm not as adventurous when kiting alone...
Most of the kiting seems to happen around Conception Bay South, several hours drive from Gander, I unfortunately didn't get the chance to head down there when winds were right so I can't speak for the conditions.
If winds come up locally for you, SW, Gambo Pond seemed to work but always gusty. I met one local there one day by chance, he said he'd been kiting there for 6 years and never came across another kite so in the Gander area we are a rare breed... He said locally there isn't a lot, Gambo Pond, Square Pond (if you know the accesses or have a friend with a cottage), Gander Lake he says works too but again, I think you need to know someone that knows their way around to get in and find a place to launch.
Things to know about Gambo Pond, gusty is as good as it gets (confirmed by local rider), you will likely be alone so self launch/land is required, there are some submerged and semi submerged hazards in the form of deadheads (old logs) that I found, the water has this brownish colour to it from rotted wood as it used to have a lot of wood in it from logging industry use.
Apparently if you want to take a drive to Gros Morne (worth going anyways just for it's beauty and even hiking if you've got time) the bay just up from Cow Head is supposed to be great as well.