I am searching for a children’s book I enjoyed as a kid. I believe it would have been available by the late 70’s/early 80’s.

I don’t remember the title, but I remember it had to do with a kid who thought he/she wanted to go to the museum, but then when they got there, was scared of the giant brontosaurus. I remember an image of her pulling on her mom’s hand to get away from the dinosaur. I don’t really remember what else happened, but the book might have been about saying no to things, or getting over fears. The images were quite simple, I think.