If you have a child and you want him to start with the Mac but you don't know where to guide him, I think you have just found the first application that is going to give you a good hand: OOoKids.
This office suite is a modification of Open Office created by the non-profit association EducOOo.org, which has invested a lot of effort in making this project a reality and can be enjoyed by children around the world.
It is multiplatform (it obviously includes Mac OS X), it is available in a multitude of languages including Spanish and it is aimed at children between 7 and 12 years old, although surely some younger ones will dare with it.
Link | OOoKids