Sassy if you each have your own individual user accounts then you can each have your own WinMX on each..
Heres how you do this.. you're going to need to rename your folder C:\Program Files\WinMXmine (or something like this)
Then when you make a new installation from here of WinMX it will create a C:\Program Files\WinMX folder for him.
https://www.winmxgroup.com/Allow your son to set this one up as he likes..
Now in order for you each to have your own you will need him to make his install from his own user account.. this will install a default Icon shortcut on the desk top.. for yours we need to manually make the shortcut so first thing is to delete your desktop short cut.. then open the Folder in C:\Program Files\WInMXmine you made.. find the WinMX.exe file .. right click and choose Send to.. 'Create desk top shortcut'.. now
If this all went ok.. These will not run simultaneously as Sam pointed out.. but they will store and save your individual share and incoming file locations for you.
Im the queen of multiple installs as of right now I have approximately 12 WinMXes installed on my PC, all set up differently for testing. If you dont have separate user accounts, this is still possible, you simply make sure you have the two folder names, two installs, and two shortcut icons on the desktop .. Rename one to My WinMX for yours... If this doesn't make sense just post back and I can try to explain it differently