Getting kids interested in ham radio can be difficult as it's hard to compete with all the other technological distractions these days. That being said, I have participated in a few events with cub / boy scouts and helped with a (ham) radio presentation at a middle school in Greensboro and saw a fair number of kids express interest. We would usually start by asking them to identify things that are or have radios in them. Surprisingly they didn't usually name their cell phone and you would get their attention when you mention that it too is a two way radio - which puts the topic in their realm instead of being some antiquated thing that Grandpa does.
What really seemed to catch most of their attention was the fact that you throw a wire up in the air and can use it to communicate without a telephone, computer, or infrastructure like cell phone towers. That you could run it off of a battery was icing on the proverbial cake. What we did was present it in the context of disaster preparedness. They could all relate to the power going out during a storm (summer or winter) and taking the phones and internet out with it. Being able to get a DX contact was also interesting to them - again explaining how it's just a wire in the air with nothing in between. Of course to a teenager, DX is someone in a far off part of the US, but getting an international one was extra cool. The digital modes and even DStar / DMR which use the internet were popular too.
Surprisingly they also seemed to find learning the phonetic alphabet and morse code interesting, especially when they realized they could spell a crude word and not be quite as obvious about it.
Of course, kids attention spans are short, so you'll probably need to take it in small bites at a time. If they show some interest in it, perhaps coach them on taking the technician test and getting their own license.