Chess is great enrichment because it is similar to the music community. Interest, discipline, desire to learn, and long attention span are the key factors to progress. For children "locked" into their grade-level by age, it's a great opportunity to just develop skill, no matter your age. In fact, the younger and less experienced children often make great chess team members because of their willingness to absorb and learn the strategy behind the game- before learning some bad habits. I teach enrichment chess for an after school program- the youngest often have the best attitudes!
The only thing jarring about chess tournaments is that they often keeps parents at a distance. If a child has separation anxiety or gets nervous in new situations, it's best to go and observe a tournament first so they are exposed to the environment. It's much easier to focus and play your best if you are not stressed in a new situation.
Standard for most tournaments is 1 hour, each player with 30 minutes on their clock. With young children, this is usually plenty of time- they tend to play fast.
Good luck!
