Multiple airports as extenders

We have had serious signal quality issues with interference from our wifi network, so we have multiple airport expresses and extremes to get everything working. After completely redoing the entire network, we are able to get everything working so we no longer have the interference issues, but now our devices have a slight issue. If they need to be restarted for some reason, they connect with the strongest signal at the time, which might be another extender. If they connect to an extender, then the signal does not get passed on. Is there any way for the devices to be set where they automatically default to the main extreme, rather than the strongest signal at the moment? I hate having to reconfigure the entire network every time the power flickers. Thanks.