I am not sure if this is what you are after in terms of a .308 load for your son - but if it is reduced recoil you are after (I am assuming he may be younger and you are looking to soften the recoil..... which may not be correct)
Firstly - there is an AO member who mentioned that he handloaded a reduced recoil load in .308 for his daughter in his YouTube channel. Brobee223
I have no experience with a .308 load specifically but I have has some experience in following Hodgdon's protocols for developing a "reduced rifle load" for my sons .243 as he was growing up.
I did not want him to develop a flinch, so handloaded his .243 to a 60% max load in H4895 (as per their protocol). As he matured over the years, I would titrate up the load until he began shooting full "hunting loads" the year before he began big game hunting.
Hodgdon also has a protocol for "low recoil" loads with their TrailBoss powder - I have no experience with these loads directly as the low recoil loads were good enough for my 8 year old. My understanding is that the recoil is even less than the reduced loads though.
Anyways not sure if this is the type of load you are looking too develop - but food for thought
https://www.hodgdonreloading.com/low-recoil-loads