As a father, I understand this. The amount of abilities bound to when they’re needed can be overwhelming. In the case of binding Tiger’s Fury to Shred, it really made me uncomfortable knowing that you’d allow your son to play this way, ignoring the intricacies of what’s needed to play the spec.
It’s not difficult or overly complex. Has more buttons than average. But if the mechanics aren’t considered, or even respected, Feral will punish the player like no other spec in the game.
As an 8 year old, he’s much better just focusing on a DH where he can focus on encounter mechanics. I would suggest he looks into Demonic spec where the damage windows are frequent without having to rely on Momentum (the builds have changed since Legion).
Again, while Feral has more buttons than average, looking at the examples given in your original post, you son will become increasingly frustrated with Feral. If not him, those you run with.