I don't know your son but for most 10 year olds I'd probably avoid the more spectacular parts of the trail (short legs and big steps up/down are a poor mix). I'm assuming that you're not planning on long daily distances.
Heading away from Duluth from the Castle Danger trailhead might work well.
You could camp along the Gooseberry River on night 1
Then see Gooseberry Falls on day 2 and camp at Blueberry Hill
Hike to and along the Splitrock River on day 3 and then camp at one of the sites on the river.
You'd have a lazy last morning in camp with a short hike to the Splitrock Trailhead and hang out by the lake and the State Park until the shuttle comes by on it's return trip.
Or you could self shuttle using bikes, I've done that with this stretch.
That route starts with a bit of a climb but is easy going from there to Gooseberry. Then there's a relatively gentle three mile climb to Blueberry Hill. After Blueberry Hill it's downhill to the Splitrock River. The west side of the Splitrock River is a rugged but beautiful two miles. Returning to the highway on the east side is a walk in the park.
Kudos for starting junior out on a enlightened path. With any luck he'll never haul a monster pack!
A question about your gearlist ... the items without weights listed are not taken?
Early June can be hard to pack for on the SHT. It could be cold and wet or it could be hot and dry. You might get off the trail before the mosquito hatch or might not. Watch the weather forecast and check the conditions page on the SHTA website.
I am more tolerant of insects than most folks but I wouldn't care to sleep under a tarp in a bivy and a head net during skeeter season (hovering and buzzing near my head). Your mileage may vary of course. A Tarptent Squall 2 or Cloudburst 2 or a SixMoonDesigns Lunar Duo or Refuge wouldn't cost too many more ounces or $$.
I usually bring more than 2 liters of water carrying capacity, especially if staying at Blueberry Hill (often dry at mid summer, maybe not in early June ... check with the SHTA website and/or hiker group at Yahoo)
Campfires can keep a 10 year old entertained, a UL saw could be worth bringing (Sawvivor?). Be aware that with 2009's spring ice storm and fall windstorm there is a LOT of unseasoned downed wood. It can take an educated eye to know what will burn well.