These creatures have no ability to speak. They were created very different from people. Adam could speak as soon as he was created. One way to help children understand this is by using a computer. Explain to them that man makes a computer so that the finished product will carry out certain commands.
Some computers even respond with words.
For instance, you can now purchase a computer that reacts to your voice. However, computers can't talk like humans they will only do what man has programmed them to do. If man can do this, we should have no trouble understanding how the infinite Creator, God, could create the brains of Adam and Eve already programmed with a language. Remember, Adam and Eve were not born as babies and then learned a language like we do today. These first two people were made as mature human beings they had to teach their children the language God had given them.