You would need two nics in the server to pull this off, but it can be done. With routers as cheap as they now are, you would be far better off simply running a router. Allow the router to handle nat. This also solves the problem of the IP addressing. Considering how few systems you are running, I would not use dhcp. Just assign static class c addresses to all of the systems. This will keep your configuration very clean and easy to manage. Unless you are planning to run Active Directory it would also be possible to not have a local dns server. The whole idea is to keep the network as simple as possible. For under 100.00 you could certainly make life easy for yourself.
