Grown children are harder than small children

I'm not sure what to start, but I will just get to the point I'm having trouble understanding and could use some feedback.
Last Saturday my husband and I were going to take our grandson to a state fair 2 1/2 hours away. Stay the night there and come home the next day. My daughter said she wanted to go as well. So my husband and I thought it was only fair to ask our other daughter if she wanted to go with us. She did. When it came time to make plans as to when we were going to leave my 2nd daughter had to leave late morning and leave the fair early the next morning to be somewhere at a certain time on Sunday. All in all it didn't give any of use much time to spend at the fair. So my first daughter got angry and said alot of hurtful things to me about her sister and why was she even going. To make a long story short, my husband I and just cancelled the trip and said we weren't going because of all the bickering back and forth. My daughter agreed and said her son was too tired and had a long week anyway and that they would stay home. We ate our hotel reservations as they weren't refundable.
Now our daughter will not talk to my husband or I because she is saying we broke our grandson's heart by not taking him. Is that really fair to us? I guess I'm struggling with the fact that we were trying to be the nice/good parents and all go to the fair as one big happy family...haha.. and look where it got us.
Also, in a week we booked a vacation to go with my daughter (that won't talk to us) our grandson and our son-in-law. I really don't even want to go to this.....but do I let my grandson down again.
Any responses would be appreciated.

It sounds like you let one daughter dictate the plans for the other 4 (5?) people. If she had to get to the fair late and leave early she should have stayed home or else driven herself in another car. The rest of you could have gone and enjoyed yourself. How old is your grandson? I'm sure he was disappointed but he will get over it. He'll get a chance to do something else with you and things will be fine.

This is just one of those family things that did not work out. Everyone is disappointed but you should not blame yourself. You did the best you could.