Agree with letting your son pick out a rod he likes, with some insight from you. I wouldn’t go with anything longer than 6′ for someone that young and small, something that has a fairly soft tip, but good backbone.
Also pay attention to handle size. Some handles are a little too big for smaller hands and become uncomfortable. And make sure the rod and reel are well balanced. I’ve held some cheaper combos that are very unbalanced (usually short rod handles) and would become very uncomfortable to hold.
Since he’s young and probably not the softest on stuff, an Ugly Stick wouldn’t be a bad choice. Kids and inexperienced anglers tend to reel fish up way too far, and reel lures all the way to the tip, so I wouldn’t spend too much money on a rod. I’d spend more on a reel that has a decent drag, since kids and inexperienced anglers don’t fight fish the same way as more experienced anglers.