Children in the Learn to Train stage should limit and monitor (children and parents together) or better yet avoid caffeine intake. Within reason, parents should be aware of the various sources of caffeine. Children should be learning these sources of caffeine as well in order to help monitor their own intake and make informed decisions about what they are drinking and eating.
The following links point to resources that have been collected and are relevant to this skill (?).
Sleep, Recovery, and Human Performance, is a 20 page pdf document put together by researchers in Calgary for Sport for Life. It discusses the importance of sleep and recovery for sport performance and some of the most prominent sleep disorders and factors that affect one's sleep and recovery. The document is very clearly and consisely written to discuss the key factors across all LTAD stages.