Cron job fails due to sleeping wifi?
I have solved this indirectly in the past several times like this:

One Mac (the one that is supposed to never sleep) has a Energy Saver schedule to wake up or power on every morning at 2:55 AM. It's set to not sleep, but it also has launchd jobs (cron is fine too if you want to maintain that older scheduling method) that SSH in to the client Macs.

The client Macs are set to allow wake for remote access, allow Power Nap (if supported) and set to allow SSH. 

We have several AirPort and AppleTV that will proxy the ssh requests and send a wake packet to the client macs if they happen to be sleeping.

The clients then can have their cron tasks scheduled for when they wake.

If you spend too much time making this work, you can instead put a backup hook into the periodic tasks or convert them to launchd and have them run opportunistically even when the ideal scheduled time has passed.