Your intro needs to explain what you are writing about so the reader doesn't have to wonder what the body of the information is going to contain.

Each idea needs to be seperated into it's own paragraph.

For example....your intro could say ( I just modified what you already had).....

Many kids desire to own pets while they are growing up. It is a huge responsibility that should not be taken lightly. This decision effects the entire family and requires a commitment to the pet for many years. This is why it is so important for you to completely consider all your options before getting an animal.

Then your next few paragraphs could be explaining some of the ideas you already have.