Can you afford to set up a CCTV camera to cover the area where these incidents are happening? You would need to make sure it is out of reach of the vandals though as they would probably just trash it. Have you mentioned to the police that you believe the incidents are race related?
I hope you manage to get these scumbags to stop harrassing you,it is the last thing you need when you have a new baby in the premises!
Congratulations on the new baby by the way,I did ask last week if anyone had heard from you as the last post I saw from you was about the headache you had when labour was starting.