Nick,
I've spent a fair amount of time fishing out of Wachapreague, but never from my kayak. Croaker and the occasional trout, and of course flounder, are probably your best bet. As far as the redfish are concerned, I'm not aware of any being caught in the backwaters up there, albeit larger drum can be caught around the inlet. If I were you, assuming the weather cooperates, I would paddle to the right leaving town and then after a few hundred yards go right again into the bay. If you follow the channel markers across the bay you'll eventually enter the narrower channels through the grass again. I've had luck with croaker there (where the bay dumps into the narrow channel and the next channel market to the east) as well as that general vicinity along the east side of that bay. It's a stiff paddle, but that's probably where I'd try. You could also try fishing along the North edge of the bay working your way east. That will eventually take you to the same spot I mention above. Good luck.
Mike