Execution of scripts in a random time during the day....

Does everybody know how to execute scripts (e.g. fw upgrade, rebooting and others features) in a random time, every 7 days, during the night hours (example between 4am and 7am) ?

I’ll try to be more accurate: i own a wisp in Italy and have about a thousand of CPE connected. I would like to perform a weekly script to achieve modifications (example disconnecting/reconnecting PPPoE sessions to update speed profiles, upgrade s/w, and other other things).

The “random” feature is useful to avoid network congestion: if I upgrade sw at the same time to many CPE’s it could slow down/crash the network or crash PPPoE radius server…

Any suggestion ?? Would be very precious…hopefully not only for me I guess.

Cheers !