Subsection 42 of the Immigration and Refugee Protection Act 2001?

Hello: Just received an email from the Canadian Immigration Authorities indicating that my husband's immigration application can be denied because we are unable to provide an immigration medical certificate for his son and daughter. Unfortunately, my husband is not on good terms with his ex girlfriend (mother of the kids). It was a particularly bitter seperation. He took her to court in Ireland to get custody and access to the children, which was dismissed and the custody, care and control of the children was given to her. We have the courts letter(document) stating this. My husband has not seen his children since 2004. The email from the Canadian Immigration states that the onus is on us to establish that Megan and Conor are not family members as defined by subsection 1 of the Immigration and Refugee Protection Regulations 2001 and that my husband my not choose to opt them out. The letter also states that given the information on file at the present time, they are satisfied that Megan and Conor need to be examined in the context of his application. We have sent a soliciters (lawyer) letter asking for her permission to have the kids take a medical examination for visa purposes. the letter stated to reply within 2 weeks. There was no reply from her or any party on her behalf. She would certainly not agree to allow their kids to have a medical examination anyways. We have received the letter that was sent to the mother of the kids from the soliciter stating what he asked her, and a seperate letter stating that there was no reply. We're afraid that this might not be enough for the Canadian Immigration. Do we need to take further action and take the mother to court? We don't want to do this because we dont have the money because we live in the UK and they live in Ireland and it would cost alot. Will my husbands application be denied if we cannot provide the medical? Will we be penalized even though this matter is out of our control? Do you advise us to hire a lawyer? Thank you for your advice.