Q: Error 3014 When updating to iOS 9 on iPhone 5C

See: If you see Error 3194, Error 17, or 'This device isn't eligible for the requested build' in iTunes - Apple Support

This error can mean that your your iTunes is not a compatible version, the phone is jailbroken, or that your computer was used to jailbreak some iOS device in the past and its network database was corrupted by the hacking software that was used. The above tip will lead you through the troubleshooting process.

It's covered in the link that I posted. You need to restore the "hosts" file on your computer.

All may be good with yours, but if your kids jailbroke their phones they are probably infected with spyware and viruses. If you share an Apple ID with them you should change every password you have ever used from the phone, and do something to undo the damage to their phones.