Glass-Bottom Boat, 1966. A Doris Day movie. It's a Cold War spy spoof set in Florida, with Dom deLuise and Paul Lynde -- not a kid's movie, though I was only 4 at the time.
My aunt from NYC was visiting, and decided that she wanted to go to the movies, and did not want to go alone. Mom said she should take me, so I went. I still remember it clearly, as it was a big occasion, I got dressed up in a pink coat, with a matching hat and gloves, and we went to lunch downtown before the movie.