8 GB of RAM are a MUST for any programming, be it UE4, Unity or GameMaker.
As for the rest, a rig that can run UE4 will definitely be able to run the other tools sso if your son wants to switch, no harm done.
I guess UE4 would be easier for your kid than the alternatives because it has visual scripting - blueprints. Basically your kid has those blocks that say “do x” and only has to link them together. No need to code.