Sorry for the lack of updates - when we haven't been super busy, the weather's been junk. So far, we've been limited to rides around the neighborhood without any trail rides.
As for the frame, it's okay. My issue that I thought was resolved with the new headset was only partially resolved. The upper cup in the frame is too big, so there's still a minor wobble. I have to figure out a way to homebrew a shim setup (pop can or something).
Frame is a 14", and I went with 165mm cranks. He was 4'8" back in March. Cranks are a little on the long side, but I knew that was a risk we'd take. Reach is great, though, and I have a short stem so I can change that out as needed as he grows.
I gave up on trying to get the BB7's adjusted, and considering it's my kid's life on the line, I felt better upgrading him to some SLX hydraulics. For now, I haven't shortened the 1700mm long rear hose, so I just looped it around the stem. I also need to install the remote lockout on the Reba.