Why do you think he wanted to leave. Why do you think his family became unhappy. Once you get to the end of this road, you'll probably be able to answer a lot of questions you've asked in this thread. If you tell someone they should look at other options, they're not going to be happy to stay and probably going to leave. You'll probably still let them coach a bowl game because it isn't quite the same as firing someone, but it is still your fault they decided to leave.