Separate Licencse X1 MK3 and S4MK3

StrictlyHighVibe

I was lucky enough to buy the X1 a few days before TP4 came out and I converted it with the new License Key on my Notebook.
Now I want to give the X1 and my Z1 to my Son. How can I switch back to the license of my S4? Will I loose TP4?
Many thanks in advance.