I would start him with casual tournaments. In our area, these are often at the local schools and have age groupings that are fairly small (ex. K-1, 2-4, etc.). They are not timed, I don't think and are a good introduction to tournament play. Our son starting playing at age five and is very good, according to adult chess players who have seen him play. He swept the local tournaments last year. Took him to a more major, K-8 in one grade, timed tournament (first time he'd seen clocks, PM me if you want a recommend on one) and he wiped out. It was a different system of play, he spent the first two games starting at the clocks, etc. Since then, we've had coaches work with him on clocks and notation. We may try a formal tournament again this year.
Info above is accurate about the timed games.
There are some great chess books and a magazine for kids. Chessmaster 10,000 is a good computer game and there are a few others.
