Hi Petronella,
I'm sorry to hear about your sad news.
My Dad has vascular dementia, and he was in hospital earlier this year when my MIL died. They'd been close as my husband and I had been main carers for both of them (her last words were "How's Tom today?"), so we decided to tell Dad. He was very upset for us, and every day for a whole week he remembered that she had died and we were arranging the funeral. Then he forgot. So we have decided not to keep on reminding him, because every time it's a new bereavement. He's also forgotten that my mum died over 30 years ago and often asks after her. The first time it happened I was very shocked and told him she was dead (because it was in the early days when I didn't know what was wrong), but now I just make some vague reply, just fine, and change the subject. You have to be prepared for the fact that they forget because it knocks the wind out of your sails the first time it happens.
I think it would be very stressful for you to have your husband to worry about at the funeral. If you do decide that he should attend, do you have someone who could look after your husband during the service?
My thoughts are with you at this sad time, love Sue x