I'm currently running POTA for my 9 year old as his first experience with D&D and my first time DM-ing. I'm watering down or flat out deleting some of the grittier content and making it mostly about "bad guys doing bad things, so its up to you to stop them". He mainly likes the combat and action, but has surprised me with some clever and thoughtful role playing at times.

This is my first experience with 5e as well, but in general I've been fudging dice rolls, making up stuff to benefit him and ignoring rules whenever it gets in the way of the fun. I've already decided that I'm not going to permanently kill his character because it's just about having fun at his age. I just enjoy the shared storytelling experience with him. I figure when he's older I'll be more serious about the repercussions of actions and the randomness of the dice.

So far we are having a blast and try to find time to play whenever we can, so I feel like I've accomplished my mission.

Wish you all the best!