No, "Just Lie" is not the correct choice.

The properly examined overprotective option is to use a service that doesn't require such age restrictions.

And I fail to see any situation where teaching a 9 year old that its sometimes ok to lie won't be incredibly confusing to the child: the child cannot differentiate between lieing here, and lieing about homework, or cheating on a test. Their brains can't do that yet. To tell them to lie here, but no where else, is confusing, and in an extension, is cruel.