I do something similar at work. I have two servers with dual gigabit Ethernet cards. The network they are connected to is 10/100Mb. So I connected the second NIC of each computer to the other. This way when the two servers sync, they go over the gigabit connection, and aren't slowed down by the switch (and aren't loading the LAN connection the other machines want to use).
In my case I gave the connection between the servers a different network address than the rest of the LAN, and no default gateway.
After a few seconds, the computers realized that connection between the computers were faster than the 10/100 and weighted the metrics to have the gigabit connection preferred for communication to the other server.
I imagine in your case with wired and wireless it should be the same.