Honestly I don't know. Thinking about it I can see that she would be mad. I just feel that if she is ignoring them and how they feel because they are kids. Then I need to protect them.
I dont know that its about being mad exactly. But your actions said "I dont trust you to take care of my kids for two days while Im gone." You say the above in blue, but you dont really know, thats information you are getting through the eyes of a 7 year old.
Of course, Im not in your situation, so you would know if there is some danger. But in my opinion, by staying home, you are showing her that you think she is an unfit mother.