Here's a short dialogue which includes many examples of future simple, going to and present continuous. It's designed to present the three tenses in a meaningful context to help students grasp the different future tenses. A true/false quiz (with answer key) follows the reading text to check the understanding of the text. The questions are designed around the specific uses of the three tenses, so it'll be an excellent opportunity to see the students on the uses of these tenses.
There's also a "matching the uses activity" for future simple, be going to and present continuous for future arrangements. You can compare the uses of the tenses with examples from the dialogue.
The online version of the quiz is here.