Also- 13 year old.
Fit or not... you never quite know.
In scouts when I planned routes we shot for a 3 route plan... high, low, medium.
Sometimes teens are best kept busy from dawn til dusk and put to bed worn and tired.
Sometimes teens are best left to find that creek to take an impromptu swim, practice building a fire, or exploring something found along the way.
A good route should have a few layers and fall back plans. Ways to cut it short or stretch it out.
Give it a 5 or 10 on day 1... there's always some fuddling around getting to the trail, playing with last minute crap at the car, or stopping for a bite that leaves you not quite rolling early as planned.
I know Ohio isn't California... but you may be a bit burned out from driving too on day 1. On Day 3... you may want a bit of time to get cleaned up, grab a meal, and get on the road at a decent time too.
Look ahead... if you do feel great and want to stretch... what could make sense on day 2.
The AT has lots of 5-7 mile increments that can be mixed and matched on the fly.
Go ahead and plan a 5/10/15 MPD set of routes. That will get you familiar with your options.
If'n you and junior are sitting there twiddling your thumbs and he's bored out of his mind- then feel free to run each other into the ground.