Macbeth may be my favorite of Shakespeare's plays. I would suggest re-reading the letter that Lady Macbeth reads from Macbeth and imagining yourself as Banquo, by Macbeth's side, during those events. How do you view the events? Where does your opinion/feeling match up to Macbeth's excitement, etc? Keep in mind, you're one of his closest friends, you've fought battles in wars together, but you're a different man than he is. A good example of this is the nighttime scene with Banquo and his son. The language Banquo uses to express himself is very different than the way Macbeth expresses himself in general.
So...Consider the events that take place in Act I, consider your opinion of them, and write the letter to your son with all that in mind.
If ever you'd like more help on anything like this in a class setting, let me know. Thanks and all the best!
