There is a way to get it done without both cardholders being there.
I just managed this. My 7 Stars companion was thousands of miles away when he got his.
It's not easy to do, but it can be done.
First, get the full name (correct spelling) and Total Rewards # of the person you want to assign as companion.
Next, find out from your TR companion which property your companion will be visiting to pick up the card.
Then go to Total Rewards yourself, and talk a supervisor into doing this for you. Some will agree, others will refuse and claim it can't be done. If you get refused, go to another Total Rewards or come during a different shift and get a different supervisor.
Fortunately I got a nice supervisor who was very helpful and said yes, without me having to look elsewhere.
If they agree, you will fill out a form with your info and your companon's info. Be sure to have that companion's info with you when you visit Total Rewards, so you can fill out the form.
Tell the supervisor which property your companion will be picking up the card at. Ask them to BOTH note your TR account to allow this, as well as e-mail the supervisor at the other property regarding what's going on.
Then your companion just needs to show up to their property, tell them to look up your TR # (make sure you give it to them), check the notes, and complete the process over there.
I got it done successfully, though there were some hiccups along the way.