Old MacDonald's Farm in Cedar Rapids is a free petting zoo that has farm animals. Our family was split on whether it's worth visiting, but it was hot and crowded while we were there which likely factored in. I think it's worth stopping if you're in the area, especially if your kids haven't seen farm animals before. If you plan to go inside the enclosures, I recommend closed-toe shoes. I saw a few people in flip-flops get cow poop on their toes.