I am not sure that they will allow you access. Your Skymiles account has your DOB attached to it - and even if you didn't provide it, or provide an incorrect DOB - when you travel internationally they scan your passport with all of that information in it. So I would assume that somehow it would flag you as underage for the lounge.

Personally, I am 22 and never have been questioned for ID or anything like that when in the CRC (or on a flight for that matter). If you were allowed access to the room though I don't think they would ask you for ID.