Interesting question, Amylou. It sounds like your kids are going to demand the scores this time. To avoid sibling issues, you could share each child's scores with that child ALONE. If they choose to share the scores with each other, they would be free to do so.
And really, is it any of one child's business how another child scores (on this or any test)?
You may have other reasons for not wanting to tell them the scores--don't want them to get complacent or boastful, etc... But that's a somewhat different issue.