execute as root:
chmod 666 /dev/nvidia*
So everyone logged on the machine will have access to nvidia device. This change is not permanent and after reboot you will have to execute it again.
If you have root access to every machine you can execute it via remote login like ssh.
You can put this line at the end of init script so file rights will be set right after every reboot.
The more elegant solution is to modify /etc/udev/rules.d/40-video.rules:
KERNEL=="nvidia*", GROUP="video", MODE="0666"
Also modify: /etc/security/console.perms.d/50-default.perms
<console> 0600 <dri> 0600 root
<console> 0666 <dri> 0666 root
(however nvidia driver does not use DRI technology the security policy is common for nvidia and DRI because the security target is the same: 3D render)
Remember that 666 file right gives full access to everybody logged in on machine so adjust this 666 example to file rights suitable for your security policy.
These files are only examples and may be different on your system. Just search:
/etc/udev/rules.d/ path for nvidia
string to find correct file to modify and
/etc/security/ path for "dri"
string to find correct file to modify.
By checking and fixing both locations there will be no need to use chmod in scripts or by hand. The modified files will be used after reboot.