There are a family of rats that have to take their uncle named “Skinny” somewhere via a boat. I believe he may be sick and they go down the river to take him to the doctor. I also think he is wearing one piece pajamas with the button flap in the rear, and either he or the driver has on a crinkled top hat. I wish I could recall more about the story. I read this book as a child sometime around 1982-1985. I would really love to get this book for my daughter.