Headless Remote Upgrade

I have a remote data center with several headless Mac Minis running Photoshop jobs on images. We need to upgrade some of our filters and other components and the requirements mean we need to do a OS upgrade from 10.5 to 10.6.

Is this something that can be done remotely using ARD? I've read a few posts about the Xserve having ARD support for similar upgrades, but I haven't been able to find anything referencing a non-server OS upgrade being done this way.

If it weren't for the 24/7 operation of the PS jobs I'd copy the DMG and follow the steps outlined for the Xserve. However, I can't risk the upgrade not working and us losing access to 1 of 5 systems for several days before we can have someone onsite to do the upgrade manually.

We're able to reboot them remotely on a semi-regular basis if one of the PS scripts fails, so I know they will boot into the OS, login and run the scripts with no interaction. I have confirmed that all hardware supports 10.6, they can actually go all the way to 10.8, but it is not necessary to go that far.

My primary concern is being able to access the systems once they have rebooted into the install screens. I think we're just going to hold out until someone can be onsite for the install. I'll test the ARD connection when I have someone at the facility for other tasks.