Just a thought but, as I understand it, you have a router and two servers connected to the internet with their own public IP addresses. The servers are inaccessible via the internet because, with your present setup, they are actually going online via the router instead of via their own dedicated access. The wireless clients in the LAN can access all computers, the router, the internet and the servers.
Is there any reason why the two servers need to connect to the computers in the LAN with TCP/IP protocol? In other words, if the servers can use TCP/IP only for connection to the internet, could all of the internal networking between the computers and the servers be done using an alternative "non-internet-compatible" protocol such as IPX/SPX or NetBEUI. That would prevent the servers from having internet access via the router while still maintaining internal network access.