How backup your Hyper-V VM's.....

There are two schools of thought..free and pay backup tools

This guy's blog shows a free Powershell scripted way to stop your VM's and then copy them to a NAS etc and restart them using the build in scheduler within windows, FREE. Matt Williamson's Blog

Or you can use this tool Free or Pay depending on what you need. Trilead software

I have not tried either of these, so use at your own risk.. just thought to point in a direction you could head.

To schedule a task on core server 2012 use schtasks.exe, no GUI built into core server 2012.

Or you could use System Scheduler FREE Version from Splinterware, has a GUI.  

There is also www.altaro.com, they offer a free version (2 vm's) and a paid version.