Based on the information provided and my interpretation of it, there are a few scenarios that this can play out.
First, it appears that the firewall is really three devices in one: a firewall, a wireless access point and a switch. In this case, you may not require the additional wireless access point, except to provide additional coverage area; however, to do this without running a long cable in the environment, it must be able to associate or bridge with the wireless access point on the router.
If the firewall and wireless access point are interoperable in this manner, then you only have to connect the servers directly to the internal switch ports on the router.
If the firewall and wireless access point are not interoperable in this manner, then you can still connect the servers to the internal switch ports on the router; however, you will also need to connect the wireless access point to a port on the same switch as well in order for network traffic to flow between the servers and clients and vice versa.
I am making an assumption here that the firewall/router will connect the internal network to the Internet and as such is an integral component of the network architecture — otherwise, you could remove it from the picture and have the servers and clients connect to each other wirelessly; however, the network would be highly contentious and probably suffer from a lot of collisions. Having the servers on the back-end with a highter throughput rate is better the better option.