Personally think. The document needs to be on hospital letterhead, preferably with the hospital's official seal and the doctor's signature. maybe more formal
After your husband's application is approved, when you and your children apply, select the option for your spouse or child under 20 years old. There is an option to upload your husband's DTV visa. You need proof of account balance in your name, not your children.
When submitting my wife's DTV, I submitted a time deposit certificate in her personal name. If your child applies, just submit your or your wife’s savings. Proof of parentage between the child and you must be provided. We have obtained the visa.
I am looking forward to your bank account opening result. Theoretically, I think it should be possible. You will also need address proof and TM30 form.