I'd be making and debugging and syspreping a golden image with all their software preconfigured before I left. This means you don't get rushed on the config/tuning and all the machines are configured in exactly the same way, you can also patch it up to the latest and minimise what each machine needs to download once you are there.
It also means that once the locals have been given suitable instructions, if a machine is virus infected or otherwise broken then they can just revert back to their "master" image.
I'd also make sure I have the following things with me.
Extra Ram (Windows 7 needs at least 2GB really even as a Web surfing box) Do you have a hardware audit of the machines to be able to determine what Ram they have/might need ?
UBCD on both Optical and Flash media (includes several partitioning/imaging tools plus things like memory tests etc in case you get a rogue machine)
Spare Optical drives (one of each pATA and SATA, if you go down the route of installing form optical media)
Two portable hard drives with the master image on.
Some spare internal hard drives (no point installing to buggered hardware, so I'd be running the smart tools against each hdd before installation and replacing it if it is suspect)
I'd also have a go at convincing someone like ESET to see if they will donate some decent AntiMalware protection. If you can't manage that then I think probably Microsoft Security Essentials is the best of the freebies, but make sure it is installed and fully up to date on your master image.