Not saying it didn't happen, but should be no reason for epoxy to cause wood warpage.  Any warpage that someone experienced (my guess) might have been due to large humidity changes after one side was sealed and one wasn't.  So I think just control the environment and you'll have controlled the warpage.  If to avoid warpage, I wouldn't worry about doing one side at a time.

I'd worry more about getting the glass to roll over the edge of the relatively thin paddle by attempting both sides at once. I'm sure it can be accopmlished, but it would seem to me the best position for glassing will be with tip up, and easiest (if you're going to try to glass over the tip) to therefore do both sides at once.  I'd wrap blue tape or packing tape around the tip at an appropriate height up the blade (1 to 2 inches?), use relatively lightweight glass, be sure the glass is on a bias to the paddle, do a lot of smoothing and strecthing by hand to get it to lay well, and use some tape or maybe hang some clamps on the glass to get it to pull tight.  And maybe it will work.

But actually, I'd just do one side at a time, and not worry about trying to fully wrap glass over the tip (beyond the small amount of glass that will probably naturally wrap as far as the tip centerline as you do each side).  This will absolutely prevent spits, and as to protecting the end grain of the tip itself, I'd just rely on the epoxy coating that will cover the tip edge (without actual full-glass wrap over) so long as you don't sand it away.  That, and then I'd avoid using my paddle to push off rocks, or whatever, as I always try not to do. 

   Thanks for the reply and reasurance. I'll fiberglass one side at a time and avoid humidity and mosture changes while I wait to do the other side. As you mentioned the difficulty of wraping the glass all the way around the sharp curve of the blade, my plan is to let it drape naturally over the edge as far as it will go and the combination of doing this on both sides will result in at least some overlap on the blade edge.