The actual booting takes place on my server though, and I want the server to supply the dhcp options rather than the router, but still want the router to supply the address etc.
i have no idea how to do what you want but i'm wondering why you want to do that.
you are running a perfectly capable dhcp server on your router, so why not just write your script to generate the complete config file and push it to the router with scp or whatever?
in my experience, two "unsynchronised" dhcp servers on a network just causes trouble. weird, seemingly random, difficult to trouble-shoot trouble.
In this case I have control of the DHCP server so that would work, but in other cases I might not. Things would work much more smoothly if the second DCHP server could respond to requests for the options it knows about. But as you suggested, I am just pushing it all out from the primary now. Thanks James