CORRECTION OF COMMON MISCONCEPTION
1) Every room key with charging can be tied to a different credit card.
2) In your case, those arriving later can tie their key to their own credit card.
3) Have them ask for a "SHARE" when they check-in. (Use this specific word.)
4) If CM doesn't know how, ask them to check the Front Desk Manual.
Example:
Mom and daughter in same room. Mom pays for the whole room cost with her credit card. Mom can have her room key tied to the mother's MasterCard for mother's purchases. Daughter can have her room key tied to the daughter's VISA for daughter's purchases.
Process:
. . . mom checks in, with her credit card, just as usual and gets room #1212
. . . daughter checks in and tells Front Desk CM this is a "SHARE" room
. . . daughter must use this exact phrase, as it has special meaning
. . . daughter uses her credit card and gets a virtual room #1212a
. . . mother and daughter purchases now go to individual credit cards
. . . one or both could pay a part of the room bill
. . . the 1st to check-in gets charges for phones or room service (system glitch)
. . . this can be done for as many room keys that have charge privileges