Okay, few questions there

First off, it's going to cost you $1000 and a ton of eUps at best.
Only SE get free upgrades for TATL flights, for everyone else it's a $500 "co-pay", each.

Secondly, see the chart (I find they keep making it harder to find) here: https://www.aircanada.com/ca/en/aco/...ade-offer.html

As E50k your Dad can request an upgrade from Flex 5 days out. If it's low flex its 21 credits, if it's high flex it's 16. Low/High is based on fare class and should be on your booking. If you want to change from low to high the change is free but you pay the fare increase (normally $$$), but you don't pay a $75 or whatever ticket change.

For you, it it's another booking he can make the request at the time of checkin or at the airport, I believe it's at the airport. Another 21 credits (plus $500) From PY you have a good chance as you're ahead of everyone else in economy regardless of status but if the seats are all gone then obviously you are out of luck.

The only way to upgrade your tickets right now, is to upfare them to latitude which is likely going to be $$$$. Latitude tickets can be upgraded at any time as long as there is upgrade space - 10 J seats doesn't mean there are 10 seats you can go into, it means there are 10 seats total. They may allocate all 10 or none as a class that one can eUp into.

Hope this helps.