Ohh..I should really bang my heads now.
After seeing your messgae, I just double checked my letter(email attachment).The last line in the letter is saying
'your children's application also has been approved'
this is the only line they mentioned about childrens application.
This is just mentioned as the last line very close to normal bla blas (data protection act etc).This is why I haven't noticed.
I think people are thinking(at least I was), individual applicantions will get their own letter(may be send to lead applicant's email address).This is what they did during ILR time.
Thank you very much for clarification and leding me in right direction.