@Ruine, what ever happen declare your dependant childrens, if the biological mother not cooperating with you for not sending them for medical, just explain to the visa office about your situation. Try to talk your ex-wife, this is for the future of your childrens, sabihin mo sa kanya na di mo sila kukunin kaagad-agad, pag-na reach na nila ang 18th bday they can decide for their self if they want to migrate in Canada. That time your still eligible to sponsor them because you declare them prior to your immigration. ANOTHER OPTION, talk to your ex-mother in law sabihin mo yung opportunidad para sa mga apo nila, huwag naman sanang maging makasarili ang ina nila, kung galit siya saýo just put in other side but for the future of your kids kailangang pag-usapan nyo yan ng maayos. Good luck