Once your routers are configured, you would just need to point your windows machines to your router(s) for syncronization via regedit or a gpo. Just remember if you use a router DNS entry to include router.name;0x1. If you use the routers IP address, the 0x1 is not required. I would, however, like to state that this may not be the best scenario. Perhaps make one of your windows server an NTP server itself.