I have never had any issue whatsoever using my TIW and someone else in the group pick up the check. When we take guest with us it is common for them to pay for a few dinners to show their gratitude for free accommadations. It seems that as long as the TIW holder is there, they will take anyone's cc.
When my friend and I stayed at Pop Century, they let her use my TIW card too. We would check out together, but under seperate transactions, and they gave her the discount too.
At TS restaurants, we just split the check. We'd give the CM two credit/gift cards and tell them how much to put on each. It worked out fine.