Start with the basics, good manners, good character, prayer, common du'a, islamic habits (eg. saying bismillah before starting good actions, saying assalamu alaikum instead of "hi" to parents and other muslims, etc.). Depending on gender, further topics can be discussed. For example, a girl at this age should start to be more aware about how she dresses. A boy at this age should be more aware of his actions and emotions (controlling anger, giving kind treatment towards parents, etc). You want to start setting them up to where they gravitate towards positive Allah-fearing people and have a strong backbone, rather than to be easily influenced by peer-pressure. They should also be more courteous and dutiful to their parents considering they are old enough to do their own chores and do things for themselves. Keep them busy, so they're not wasting their time on things that give them no benefit.