Rhino 5.6 allows you to select whether you want to install for one user or for all user on the computer. In addition, the deployment of RHI files can be scripted to happen silently.
"C:\Program Files\Rhinoceros 5 (64-bit)\System\x64\rhiexec.exe" "C:\Full\Path\To\Installer.rhi" /admin /silent
The /admin option installs for all users on the computer. The /silent option will install without showing user interface.
Having difficulty installing an RHI file? Read the Troubleshooting RHI Files article