西语 is the best choice and it is easy and the most useful one for college. If your child can finish 3 years in high school, they don't have to take foreign language classes in college, which is required for a college degree. Latin is only useful for if you want to do a major related to that. French is not very commonly offered in high schools thus not a good choice.
Chinese won't stick since they have little chance to really use it.
