I have reffed basketball and umpired baseball already. Baseball is incredibly easy. I umped home plate when I was 13, for kids that were 11.
Basketball is trickier. I reffed seven and eight year olds, so you had to let a lot of stuff go, and how much you let go was difficult to gauge. And you'd be fucking amazed at how some parents, even at that age, still take it too seriously. My favorite was when a coach walked out on the floor and started admonishing me for asking if a kid writhing on the floor in pain was OK, because I should have been checking if his son was OK because he got fouled the previous play (he wasn't injured in any way, just got bumped). I also had to T one coach up for arguing about moving picks, because he decided the best way to demonstrate a moving pick was to set a moving pick on the official. Pushing the ref is not a good idea.