I don't think that this can be done very comforatably out of the box.
The only workaround I can think of is using multiple ULRs under Titles & Properties and remove the All additional URL redirect to the default one.
Then you would need to put this page in an special PageGroup and don't show it in Navigation.
Then you would make a redirect page redirect to this now not in Naviagation shown ChildPage.aspx
Since the ChildPage.aspx is not shown in navigation you would have to hardcode the redirect page as if you would link to an external page http://126.96.36.199/ChildPage.aspx
That's the only out of the box workaround I can think of.
Another case where it would be nice if a redirect page redirecting to an internal page not shown in navigation would show it anyhow. If a redirect page is shown in navigation should be the only reason to show or hide it (external and internal)