I have ant code that kicks off a release build in all subdirectories:
Antelope Ant extensions have a try-catch command which can be used to to what you need:
....
break=false let's continue the next command after failing. But failed targets set the haderrors property which is checked in the end. I used it a lot for build jobs (and it works fine) but I am not sure it works for inside . Maybe you have to list all calls explicitly.