Decisions about elderly parents

I guess when parents are near 90, there is always an issue. As my dad's physical health deteriorates, he needs more assistance with my mother. He hopes to have an aide in the late evening to help get her settled in bed. He is not sure what to do. I offered to help settle her for the night, but my dad didn't like the idea. He worries that if something happened to him, my mother would be stuck. She would be, but only for a limited time as aides come in the morning. He suggested an alarm, but my mother would not know to activate it, so I don't think it would work. I've wondered for some time now how much time my dad actually interacts with my mother. Does he sit down and chat? I really don't think so, because he has worn himself out doing care, and doesn't have the energy. If he doesn't interact that much, then perhaps it is time to consider a group home or assisted care for my mother. I am trying to remain peaceful, but every non-eventful day now is a gift.