I'm always tempted to push people into programming. Mostly because I wish I had learned it in high school instead self-teaching in my mid-20's.

But really, at their age it's mostly just important that they try to make something. Doesn't really matter what it is, or if it's successful. Just pick an idea and fool around with it for awhile. They need to figure out what they like and what they don't.

Writing: 1) Research papers on topics researchable on the web, and 2) Short stores. Here's an exercise. Submerse yourself in the writing of a favorite author for a week, then rewrite a story by someone else in the style of the favorite author. Repeat for 3 different authors and without trying you will have developed a style of your own based on what you like.

Striking a balance between consuming and producing. Creative endeavors are lifelong skills that add ease and finesse to other domains of life. Get them thinking about how to make stuff.