If your father plans to exceed the UA Y allowance, I would at least try to check the bags without comment, and if prompted for payment try to argue that it is a business class ticket (which, in terms of the underlying coupon, it is). I think you have at least 60% odds of that working; UA routinely does this if any UA segment is in a premium cabin. (Also, MSP-ORD probably has a decent shot at clearing off the waitlist especially if a 739).