It's called "holding out hope", not going against her wishes. Obviously Disney is something the OP loves and wants to share. I haven't seen anyone suggest NOT consulting her about taking the children.
I'm sure I'll get flamed for this, but I would totally ask the grandchildren if they want to go-as long as you are footing the entire bill for them. If they want to go, you'll have already overcome her objections. BUT, be prepared for a backlash from your daughter..
If you want to go more subtle, I would totally play the "I don't know how many trips I'll be able to take" card. Use your age to your advantage, otherwise, what's the point of being old?
So, ignore the daughter, then try to rally the kids against her, and make the trifecta with a guilt trip?
Booking anything against her wishes is going against her wishes. OP said in the original post, she objected and they booked it anyhow, with the expectation that her opinion would change.
The problem is not the destination, it is the OP's approach. the more I think on this, the more I think that's the real problem.
Would you see it differently, if the OP was a teacher, and the destination was dangerous in some way?
I'm not flaming you, but I really think your approach would just add fuel to the fire.
I think a far better approach would be to find a compromise the daughter likes. I mean how bad would it be to rework the trip in a way the daughter/kids would like? You catch more flies with honey...
Maybe they could find a wonderful compromise. Disney is close to beaches (TWO coasts!), tons of parks (national and state!), tons of amazing historical sites (St.Augustine) , educational sites (NASA, Tampa Aquarium), Daytona (the 500 is right about that very week!)
Maybe if the OP simply asked, the family would agree that a trip to Daytona/Kennedy Space/beach/aquarium would be amazing, with maybe a compromise short visit/day trip to Epcot.