We're looking after a 4th dog, another oldie.... any tips???

[EasyToEatTiger]

We're normally a 3 dog household, 2 oldies, both about 14 15, and a 4 year old, all collie types. We have had some problems with the dogs, 14 & 4, the elder coming out worse. This is a problem in itself. We are just looking after an oldie for a friend, who's a 13 year old bitch. Our old bitch is fine with her. It's a problem that our oldie bitch is losing her continence and the newcomer is unsettled. The boys are sorted one way or another. Has anyone got any ideas about how to settle the girls or how to cope better with dodderiness?