This should be real easy, but I can't quite seem to figure this out.
How do I setup a simple DMZ to an internal IP Address..
My son wants to host minecraft with his buddy…
(it would be nice to turn it on and off easily)
A DMZ is a separate isolated network from your LAN. What you want is a NAT port forward. Go to Firewall - NAT - Port Forward and add one for TCP 25565. Set the Redirect Target IP to that of your son's server, and Redirect Target Port to 25565.