Hmm, I am really not sure if the G1 jockey game is available in the US or not, if not, it is coming soon. I would suggest looking wherever you shop for games at to see if they have it, or any of the games I listed. Just shop around, you should be able to find a horse game that is not really childish, just look at the cover or the back, see if it looks childish. Some game stores also have a TV, computer type thing where you can scan the game, and it gives you pictures of the game play, and descriptions.
G1 Jockey, My Horse and Me, Ellen Whitaker's Horse Life, Imagine Champion Rider, Mary King's Riding School 2.
These are some horse games for wii that are not too childish.
are those compatible with a US Wii system? i've heard that G1 jockey is only compatible with UK and Japanese consoles.