Welcome AACL, thank you for telling us about Georgina - what a beautiful name . I'm 2 years down this road and my darling ds was 15mo when he died. I'm so sorry to hear about your dh too. You really have been through so much. Come and have a chat, cry, laugh, whatever you fancy
Crumpette - don't worry about the 8 week check, that can wait (unless there is something you want to discuss with the GP).
Did you explain your position to the Registrar about getting ds registered asap? If you did and that's still the earliest date you can get, phone or write to whoever sent the letter and explain the situation. If they're not happy, tell them to contact the Registrar direct.
I've got a feeling I had to call the Child Benefit people myself. They were very understanding. Explain the situation, even if you do have to pay the money back I very much doubt they will get arsey with you.
I don't blame you for putting these things off, I think I was the same. But they need to be done. If you need some hand holding we'll be here. Anyway, I can't talk, I still haven't sorted out all of C's paperwork type stuff.