I have a two year old daughter an four year old son each have a miniature horse that they ride and take care of. My son who is fairly into the whole horse thing is outgrown the mini. Should I move him up to a pony or go straight to a gentle saddlebred? I'm planning to put in a round pen for him to get more comfortable with riding. I like the idea of a welsh or larger pony but it won't be long before it would be outgrown. My daughter who I'm sure will set the barrel racing world on fire one day is very small an likes the minis. I really thought this was going to be a bigger deal to my son but not so! I know I'll have many years of riding with her and I think his interest will increase when he can get out and ride the farm. Also what's a good size for a round pen? Thanks.