The photo book is right up her alley, I am kind of hoping she will break out of her shell at Disney and let loose a bit! She would never do a face paint and says she won't go on many rides. I wish she would celebrate her cancer but I think even having a dessert delivered or having a Cm wish her well would embarrass her. We never got ot that stage of I beat this now I am am going to conquer the world! Lol.
I have never had Cancer but lost my mother to Lung Cancer. Even when things looked good during her journey she said "but I will always look over my shoulder worried it's coming back and will beat me next time."
So I'm sure that might be part of her fear to say she beat it.
They have a generic button that I wore when I went to Disney with my elder friend/adopted Mom. I met her after my mother died and mentioned I wish I would have been able to make a trip with my mother. So she said "well I don't have a daughter so take me for my 79th birthday" so I did.
She wore the birthday button and I wore the "I'm celebrating" button that I wrote "LIFE" under the "I'm celebrating". I had a few CMs ask me what I was celebrating and I kept it simple and said life.
Maybe you could wear one that says "I'm celebrating the love of my mother" and let people see how proud you are of her without having to tell her story.
My husband and I don't like people making a big scene over us. We especially don't like the birthday clapping in restaurants. So I can understand your mother not wanting to draw attention to herself.
Maybe you could wear "Celebrating FAMILY time".
Disney is Magical and you just don't know what will come of your vacation.
Don't worry if she doesn't want to go on the rides, there is so much people watching she can do while waiting for you. She just wants to spend time with you and watch your children smile and be happy. Get pictures of that. Make the focus be on the kids, and you, but squeeze her into the picture.
They will be priceless to both of you for many many years!
Go and enjoy. I'm sure for her it's just being with you all that is her celebration. Be ok with that and let the magic just happen.
Wishing you

and lots of magical experiences.