Well, after being at my local shooting area today with my 10 year old son and his friend of the same age I should ammend my earlier statement and add some extra input.
My son, who has limited recent shooting experience since we as a family are just getting back into the activity, was fine with factory .38 loads in my 608. In fact he was touching off factory .357's within the first 6 rounds. Both were 130 grn and 125 grn UMC's respectivly if you care. Of course I have the 6.5" barrel and ported so that should be considered. With .38's muzzel flip was slightly wild, but he could control it. With the .357's flip was very noticable and he was aiming 2 feet low at 14 yards to hit the target because of it. The recoil wasn't an issue to him with either load. He was a little leary of the .357's until the first round but after that he shot another 99 rounds of them compared to the 20 .38 rounds he ran through it.
The only real issues I noticed were he had trouble with the frame size, weight, and trigger weight in DA. He couldn't quite get his fingers on the trigger enough to pull it in DA, half because of the reach and half due to the pull weight. He also told me that holding up while aiming was hard, it's not always that easy for me either, 3-1/2 lbs at arms distance gets tiring.
If I were going to get him his own I would feel ok with a med frame in .357, SA or DA, probably 4" ported barrel.