Choose a special event and write a letter inviting a friend.
You made it fun! This should involve sketching a brief outline from which to work from rather than a comprehensive detailing of minutiae. Whilst there are many similarities a formal letter should always be considered as a document with a real purpose and ramifications.
Would he ask for payment for the broken chair?
While students may protest that they can accomplish the task much quicker by word-processing, another benefit of handwriting a letter is that the speed becomes almost meditative. But care should be taken to make sure that all the questions in the original letters are answered.
Examples can be easily obtained from local newspapers or from children's magazines such as DK Find Out or Aquila. To do this it is helpful to employ some rhetorical devices to make the writing more persuasive.