Hello Charlie, I'm so sorry to hear about your dad.
My dad died three years ago, and although we told my mum and she was of course, very upset at the time, didn't remember that he was gone. I took the decision not to keep telling her as it would come as a shock and upset her anew every time.
On the day of his funeral she had to be told again, but by the time we got to the service I think she had forgotten again and wasn't overly upset. Afterwards, she enjoyed seeing all of the family, they didn't crowd her but came to chat, and afterwards she said she had had a lovely time..... so really, you have to go with your instinct and how your mum is, as you know her best. I found it more stressful I think, being upset myself and worried that mum would be too, but I was relieved afterwards as she seemed to cope well, probably because she couldn't remember. Had she not had AZ she would have been dreadfully upset, they had been married for 64 years
I would see how your mum is and if she is too confused and worried, then take her home. This may be worse later in the day if she is 'sundowning'.
I hope all goes as well as it can for you all. Thinking of you xxx