If I made a reservation for someone using my miles, can I check them in (and pay for their bags) or do they have to do it themselves? The PNR is in "my trips". I've been able to make changes to their trip, change seats, etc., but just wondering if I can actually go through the check-in process for them.

And to extrapolate on the reason for wanting to do this, I want to use a credit card that has an airline credit (Amex) - NOT BofA Visa which I know only gives a free checked bag for pax on my same PNR. If I can, then I will ask on the Amex forum if my airline credit will be good on pax with different names than me.