I just read the terms for the Maple Leaf Lounges and it says that *G may access the lounge on the same day as travelling international on a *A flight.
It also says one guest is permitted complimentary, as long as they are flying *A the same day internaionally. It also says that that there is a fee for additional guests (either $10 CAD or $20 CAD depending on the time of day).

So I guess I will be able to take the 3rd guest with me, for a fee.