Hi LizardBottle,
For help with sending FaceTime call links to an Android, are you able to send as expected if the contact is added prior to sending the link? The information below found in the article here has some additional details to assist. Use FaceTime with your iPhone or iPad - Apple Support
"When you tap a person's contact information, FaceTime tries to connect using any FaceTime-enabled phone numbers or email addresses you have stored for that person. To avoid placing calls to unintended recipients, make sure your contacts are accurate and don't contain old or unused information."
If needed, the guide here can help will adding the contact prior to sending the link: Add and use contact information on iPhone
You can also test when the restriction is completely off to further isolate. Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
Should the issue remain, reach out to Apple Support directly to further assist.
Get Support
Contact Apple for support and service - Apple Support
Best.