Hi NZFlyer,
The inventory that you see on the website is exactly the same as what you'll get calling Aeroplan. It is pretty hard to get D class (award J) to HNL if you have no status as they only have 1 flight a day and only 25 total J seats available. If you feel better calling in, you can "act" as your dad as I am sure you know all the info that Aeroplan will ask you about him.
Btw, even if you book award travel online, you still have to call Aeroplan to confirm.