Passing through Vancouver with a layover of 2 hours to fly to Japan

Hi everyone!

I'm a bit worried about my situation. I'm flying to Japan (passing through Vancouver with a layover of 2 hours) from the 10th of July to the 27th of July.

I'm flying from Mexico. I have both mexican and spanish passports. Here is the problem:

I was planning to just go with my Mexican passport, since it's a layover, but I just learned you still need a Visa (ETA).

If I use the Mexican passport, can I get the ETA? or I forcefully need the Tourist Visa? (I'm scared it's not enough time to get it)

My spanish passport expires on the 16th of August, and since it doesn't comply with the 3-6 month period it has to be valid, I don't know if I can get the ETA and have any trouble during the layover.

What would you guys do?

(Sorry about my english)