My mom is a hundred. How should we celebrate?

You know your mother and what she is capable of better than we can, is your sister being being overly pessimistic or would the fuss truly be stressful for your mom? People in my area often hold open houses for significant birthdays, usually the facility makes the common room available and will supply beverages. At my mom's nursing home all birthday celebrants got a cupcake and staff sang happy birthday at lunch, so there was no option to pretend it was just another day - frankly I found that heartbreaking. On her 99th I arranged a picnic lunch with our immediate family because I couldn't bear to let the day go unmarked, the party was brief and as stress free as I could make it and we all came back to my house for cake and coffee as mom headed off for her after lunch nap. By then mom was pretty much out of it and I'm not sure it meant anything to her, but it was the last time many of them saw her alive and I'm glad I did it.

Could you read my post on another question:

https://www.agingcare.com/questions/my-mom-suffers-from-alzheimers-she-is-turning-90-and-im-not-sure-how-to-celebrate-her-birthday-448249.htm?orderby=recent

Try to understand why your sister thinks it is a bad idea, and work around it!

Your sister is focusing on what would be best for your mother. You say that your mother is in a care home, and your profile states that she has dementia. If your mother might become confused or frightened by the sudden appearance of people she doesn't remember and can't place, inviting the family wouldn't make a very happy birthday for her.

You have quite a while to come up with a better plan. What about asking family members to contribute cards and photographs, and making a nice, clear montage that you and your sister can share with her on the day?

Cake is always good, though :)