I thought the exact same thing as you. Regardless of the breed, a THREE year old horse/pony/donkey will not have the experience to carry an inexperienced rider thru pony club, especially when 75% of the kids who attend PC are usually more an inexperienced group(no offence to anyone, I was in Pony Club myself for years, great program).
If he carries a kid thru it, it's likely more because as posted above, he is a saint because he is to young to have had the proper training or even the experience to take on a beginner rider.
With some training under it's belt, you could make yourself a very good amount of money. If you decide to sell your pony now, unless it's a little horse with exceptional conformation and breeding, you are not going to find someone who is willing to take on a green welsh pony unless you price him for cheap.
Would be curious to see pictures of him.
As for the OP, I would have to agree that pony is a saint