Hello and Welcome to BYC
From a parents point of view, if your son is responsible it should be pretty easy. Chickens don't need a lot of attention. Just food, water and a place to live. They're not care free, but easier than some other animals.
They WILL eat everything green in your yard they can reach, dig dust baths where they want them not where you want them, and the coop and run will require maintenance. How much depends on whether you let your birds range or not, the litter you use, how big your housing is for however many birds, etc.
We have:
9 chickens, a rather large coop that I can stand in to clean up, use deep litter in the coop on a dirt floor, and let our chickens out in our yard all day.
I cleaned the coop litter out six months ago, hoping I can stretch to a year this time. Weekly I dampen the litter, after scraping the roost and loft of any poop, and stir the litter with a rake. It takes maybe 20 minutes.
Chickens are a great choice for a kid. Chicken TV is great for the whole family.