I haven't decorated, I only have to give 1 present, mom doesn't really understand holidays as far as I can tell, but at least she's pretty healthy and pleasant.
The home had a holiday party last week and she seemed to enjoy it. My brother and my nephew came for dinner also. We all had great food, the home had music, all the families came and there was lots to look at. Santa also visited with presents (that we had purchased for our loved ones prior).
My aunt sent my mother 2 of the read aloud books for people with dementia by Lydia Burdick. We sit together, I read and point out all the little details in the illustrations. Really great books, I believe they're available on Amazon and the Alzheimer's Store. The one she likes best is called "Happy New Year To You!" and it goes through all the months in the year.
Here is a picture I took just before the party started. The big dog she is holding was a gift from my brother.