If I could go back in time and help prepare my 16 year old self...I would learn how to program. This is an absolutely necessary skill in genetics, and pretty handy all around. Python and Unix are the best places to get started. I recently found rosalind.info, a site with tutorials and practice for biological computing. Besides that I'm sure there's more fun entry-level stuff to find online.
Microscopes are great! I think a small handheld one would be great if they have access to an outdoor park/pond place. I have a lot of fun looking at my moldy food using a celestron USB microscope.
One book that I really enjoyed and got me excited about science was the graphic novel adaptation of Darwin's On the Origin of Species - http://www.amazon.com/Charles-Darwins-Origin-Species-Adaptation/dp/1605299480