Another great pony breed is a Pony of the Americas (POA). I've never met a POA that I haven't liked. They come in a few different sizes, from very small to practically horse size, and the medium to big ones are definitely sturdy enough to be ridden extensively by adults so that you can be sure that it was really trained, not just ridden around by a small child like a Shetland might have been.
Another plus to them, is that the ones I've spent time around were almost Arab like (that's the only breed I can think of that is known for it's devotion to one person, no prejudice in this statement) in their devotion to their person. They seemed to meet one person that they clicked with and remember that person for the next forever. One did that to me and he would ignore EVERYONE around him, no matter what, to get my attention and focus on me, even if I was half the barn away. He would stand there, surrounded by people brushing him, with his head and neck craned so that he could watch me, where ever I was. He could have cared less about the people around him, it was all about where his "Mom" was. I could imagine that being an excellent trait for a kids pony, where the pony adored the heck out of the child.
They're a good all around breed and evidently there are a lot of breed shows around that I've heard are generally very family oriented, if your child ever became interested in showing. :)
Also, I've heard of Shetlands being evil and I haven't been around more than about 3 of them but I've never met an evil one. I'm sure they could be evil though, I've heard enough evil pony stories to not discount them.
But, there's an exception to every rule!
Anyway, giant post over! Good luck in your search!