Unmaxdemax : Hopefully you see this.

Areoplan agent was incorrect in saying you cannot guest to the Cafe. From the AMEX T&C on the AC website:

Basic and eligible Supplementary Cardmember(s) are each entitled to offer one (1) guest complimentary access to the same eligible Maple Leaf Lounge or Air Canada Café.

Unfortunately another case of AC staff not being properly trained or being advised of changes.