Assuming you can change fares that's probably a good use of your Prestige SWUs. If it will get you to Elite, I think you'll get some more when you get your Elite package.
Upgrading on Canadian routes earns a lot more q-miles now. YYZ-YYC return on an H ticket gets about 1676 q-miles, whereas if you can upgrade using certs you'll end up with 4,188. Plus 1,000 for flying out of YYZ gets you over 5,000.
It looks like your flights both have C space available right now. I suppose you could always phone at the 2 day mark and pay the change fee to get onto a flight where you could upgrade if necessary too. Does an H fare allow that?