You may be better off creating a paper wallet and store a digital copy on usb or microsd.

The Raspberry Pi series are great little devices.  It suffers from one big flaw.
It has no power management.  This means that you could potentially end up with corrupted files/filesystem.
I've had sd cards killed multiple times because of improper shutdowns due to power outages.
 
If you choose to continue with the Rasp. Pi Zero just make sure you backup the wallet on a regular basis.
It can still serve your purposes, just be aware of the above and take action to keep proper backups.