A stainless rifle will still look good 20 years from now, even with a kid not taking care of it.
Kid's hands often have lots of acids that can rust a gun pretty fast, if not taken care of. If you don't buy a stainless gun, coat the metal parts with a good automobile wax or synthetic protectant like Turtlewax R21.
A rifle with a good tubular magazine feed is easier for kids to load and they hold more ammo. Some box magazines have very stiff springs and lower capacity. It's also harder to lose the tube than a box magazine.
Lever actions are good, but Henrys have a sleeved action that doesn't seem be amenable to scope use. I don't know if they do well with receiver sights either. Still, they're a very nice starter rifle for kids. Marlin 39s are quite heavy for kids to hold offhand and mine has had more than it's share of factory defects.