I do this with my packages if the box is sturdy - I do as you said and tape a piece of paper on one side with the address, etc. Make sure the box is taped securely. I mail routinely to Japan and there has never been any problem.

If you are unsure - you can alway use cut up paper bags - but I do not bother if I have a good box - nobody has ever cautioned me about what the box says

Catalogs also mail things out like this - all the package information and pictures etc - with nothing but an addressed package slip taped on - so you should be fine with the way you have done it

I am not familiar with Canada though.