Hi I have been in the same position you need the childrens father to sign his consent for your visa. If he is willing to do this then no problem otherwise you can apply to the courts to ask them for permission to take them. We move on 8th April 2013 to Perth but am leaving my 15 year old daughter behind to finish her GCSE's (she is at grammar school here in UK and she didn't want to leave school here) she will reside with her father (he refused to sign any documents to even allow her on our visa until she is 16) She will be out for a holiday in July and then as many hols as possibly until she decides where she will do A levels and Uni. I have 2 other children now of 8 and 6 and myself and hubby are fast approving 45 years old and feel we can't delay emigrating any more we just hope my daughter falls in love with Oz and wants to eventually make the move!!!! Good luck with your visa process
Christine