Computer addiction will likely be more of a challenge. This has been exaggerated into a lay belief that adolescents think of themselves as invulnerable. Even if they think that computer addiction is possible, they will not think it likely to happen to them personally. They are more likely to make the attribution that those who are addicted have some personal weakness that they themselves don't share. This may be the most difficult proposed issue to address successfully.
Plagiarism is also quite tricky.
Even college students have trouble understanding why this is proscribed. These are issues that 9-12 year olds can understand. Personal identity is somewhat different than the other proposed issues. After this time, children have more abstract, differentiated, psychological, and objective conceptions of human personality and relationships. Hence, this issue may be a challenge as well.