My son who's not yet 4 learning to use a hitch. He thoroughly enjoyed this little adventure in a small Maple across from our house. Thanks @Brocky for the recommendation on the Fraggle ii harness!
My two older boys just turned 3 and 5 this summer; the 3yo just likes to clip in and swing around but the 5yo is fearless. I set him up with a Michoacan on SRT (no RW due to his weight) and a foot ascender. He'll ascend up 6 or so feet (I won't let him go out of reach, although he begs to, in case he gets spooked) tend his hitch on the way up, and then take the ascender off the rope himself, hang around a while, and descend down. Proud papa moment for sure! I should try what you did and hoist him higher with me above him. He'd love to descend from there.
We have one Singing Rock Kids and one Wild Country Vision full-body harness for them and really like them. Slight preference to how the Singing Rock fits but both do the job well. Who makes his harness?
This harness is made by Edelrid. It comes in X-small and XX-small. My son is pretty small at almost 4 and only 31lbs and this is almost too big for him which is good because it will fit him for a while. I liked doing this set-up as DDRT with a friction saver because he can use the hitch with almost no risk but can still go fast if I let a little of the tail out in advance!