Ubuntu Networking :: TCP/IP Settings For An Isolated Network?

small non-profit set up an isolated network for a classroom, not connected to the Internet. Most of the computers are old second-hand systems, made usable by running Linux, the one new computer can dual boot Ubuntu and Windows. I think the most light-weight approach would be to use one of the network numbers reserved for private use, assign static IP addresses, and host names in a hosts file, rather than relying on DHCP or DNS, because this wouldn't rely on any servers. But, even so, I expect to have to configure _something_ for the IPs of a gateway and DNS servers when we set up the static IP settings.what would work best for these settings?

The best guess I can make would be to list a real system with a tcp/ip stack that wouldn't be too tightly firewalled, so that requests would get promptly rejected (or handled if there is a trivial way of doing so), rather than timed out. But, I'm looking for more specific advice of what works on practice. (I'm familiar with other flavors of Unix/Linux, and TCP/IP in general, mainly from running applications on servers, but I don't have much experience on Ubuntu.) These systems would be on Ethernet switch, but I don't think we can count on any router appliances. I suppose one of the spare computers could be dedicated as a minimal router. The objective of all this networking is to set up print sharing and perhaps file service, using one of the better computers as a server.