We had a similar problem, as we're 2.5 hours from the GTA by car, and we didn't want to make the trek all the way to the Toronto area only to find out they didn't even have what we wanted.
So, I ordered off Disneyshopping.com back in the summer, just after we booked our trip for January. They had a huge sale on ($5 t's, regularly up to $15 each) with lots and lots of selection, and a super big size range (even ones big enough to fit my 6' 4", 3X hubby).
We ordered 14 shirts in total, for the same shipping fees as if we ordered just one item, so with ordering so much it became not such a bad value. Now, when we ordered our shirts the exchange was no where near as bad as it is right now (I think our dollar was worth around 90 cents then) so that would make a difference.....but with the exchange, shipping, duty, taxes, etc. all in, each shirt worked out to just under $11 CDN. I have my doubts we could get Disney t's in Canada for $11 tax included! (and I would guess the Cdn stores would have no where near the selection that the online store has)
Anyhoo, they have some great specials from time to time if you keep an eye on the website. Price it out and maybe that's an option for you. I think right now there's 25% off everything you order.......and if you're planning a trip in the very near future, maybe you could have the stuff shipped to your resort to save the international shipping?
Hope this helps