The first Christmas after a bereavement is always difficult, my suggestion would be not to spend it in your own home, but to do something different.
You say the family want to do whatever you want, but you don't know what that is.
So, tell them that and ask them to surprise you.
I am sorry for your loss, please, don't feel guilty. We all do and have regrets when we lose someone, but usually there is no reason to feel like that.
Estranged Son and Future Granddaughter
To think that London, or anywhere else for that matter, does not belong to any one demographic