How sad for all of you. Be assured if the school your Gc are in felt there was a problem they would act upon it and are duty bound through safeguarding. As said above they couldn’t give any info out. Each child has a UPN ( unique pupil number) and this will have been given to a new school and schools share information about new pupils. This number was established so children don’t just disappear from the system or appear with no background.
The CAB will give you accurate advice. I would be very wary about a police welfare check as although names are never given it wouldn’t take a genius for him to think it was you.
All you can do for now is look after yourself and your husband. You don’t say how old the children are but they are together and in time things may change. It may be you could also send copies of the letters you have written via your solicitor to his, to be given to the children if anything changes in their family circumstances, as their Guardian.
Love and prayers ?
Tales about "stingy" guests and hosts.