I chuckled when I read this. Animals do not sin. Nor can they. This is because animals are not spiritual beings, but we humans are. Animals are, of course, limited to the Limbic brain system and only do what is in their nature. As spiritual beings humans can choose to go against what is considered moral or righteous. This is the distinction between man and animal.

While we are not gods to animals, God has given humans dominion over animals. This does not mean that we should be cruel to animals, but rather enjoy them or make use of them according to their abilities.

And yes. There must be animals in heaven. I believe that a pet that is loved does go to Heaven. Even a dog who once chewed up your shoes.