Are you using the second wireless AP as a bridge, meaning your Internet connection comes in on the other one, and then you're using the second one to get ethernet to your mining computer (it's bridging the two points with WiFi)?  If that's the case, then you're really not doing ethernet, you might as well just run WiFi on the computer mining and be done with it.

Personally I would replace whatever is taking down your ethernet - if WiFi is more reliable than ethernet, something is seriously wrong with your setup and you're better off diagnosing that then trying to do some sort of failover to another connection.