I don't understand the reluctance for your Dad to apply. First year is free, and $200 in bags would cover years two and three (assuming he doesn't ever fly again). Cancel it after 11 months if he's not a frequent traveler, and you're ahead of the game.
The default offer on the Delta/Amex site is up to 30K btw:
https://www.deltaamexcard.com/Offer/BL5.aspx