How to configure delay for childs when Parent host comes up?


Imagine this situation: When power blackout occurs, and router & server go down… Nagios shows: Router Down, Server- Unreachable. Then, when power is restored, router comes up. Nagios will say: Yes Router is up, so I can check all childs now. But server is just booting, so its offline for next let say 5min.
Nagios will change status from unreachable to Down hard state and send notif. immediatly.

My question is, how to avoid this situation? I don’t want receive emails from child hosts for let say next 10 min. when the top host comes up. Or better, I don`t want to check childs host for next 10min. Is it possible? Maybe I can use events, but don’t know how…

Many thanks for any suggestions