Ouch. From working with PXE, I can tell you that if they are a bunch of different machines, and they're old, you probably want an accident to happen to them so they're destroyed rather than trying to make this work. If they're the same, you might have a shot. The reason is that older machines have many firmware issues with PXE, before you even begin to worry about the OS, or the wireless.
The only way I've done this using by using products such as Ardence BXP. (www.ardence.com)
. Even then it was difficult to do dependent upon the network transport. Sorry I couldn't be of more help.