Sanibel is a gorgeous island
You will love it there! It's only a few minutes from Fort Myers too. I still can't walk on the beach at Sanibel barefoot, and I am a Florida girl. LOL
It hurts!! There are sooooo many sharp shells. Naples is gorgeous too. There are some hotels on 5th Avenue and near the beach. I don't know if the hotels are dog friendly though...I can't remember.