I learned on a bolt action .22 - a remington sportsmaster I got when I was 10 - and 20 years later I'm still not bored with it.
When I was learning/practicing as a youngster I recall fantasizing more about being a sniper - making each shot perfect - than about shooting lots of bullets. Getting smaller and smaller groups, and then shooting at smaller and smaller things (trying to shoot a stick in half etc) kept me interested... well still keeps me interested.
I like my pistols, and I've had a lot of fun shooting AR's and other "exciting" guns, but that remington is still probably my favorite shooter. I don't think you have to worry about the boy getting bored, and you can probably find something great for ~$150.
I'm not saying you shouldn't get him a 10/22 - they're great little guns too - but I just wouldn't eliminate bolt guns because they're boring.
si vis pacem para bellum