Personally, I say forget celebrities, TV, etc. Mythbusters may be fun, but that damned hat is completely inexcusable
While my generation had Beakman (of course, less serious but great fun) and Bill Nye, what personally got me fascinated in science was my father.
We did all kinds of fun, magical things together when I was growing up that were hands-on and FUN (which was wonderful) but which were tied closely enough to science so that as I grew I could learn more and more about a concept or field that had been introduced to me in an impressive and usually very tangible manner (way more wonderful).
For example, he and my brother and I would build and launch model rockets (well, until a certain age, we read the schematics and handed him pieces, but the 'fun, tangible, attention-grabbing' part is of course launching the finished project).
When I was maybe 6 or 7 he got me a little microscope for my birthday or christmas or something and we scooped up pond water from a little pond behind our house and I had my first look into the microscopic world. It really gives me chills to think about it now actually; it's so powerful seeing bazillions of little squiggles all moving around in there. It's even more powerful when you're informed that they're all very tiny living creatures living out their existences; I can't think of a more powerful, direct way of showing a child that there is much more to our world than what directly meets our senses.
Finally, STARGAZE with them! If you live in or near an urban area, take regular trips outside the halo of the city and talk planets, constellations, galaxies, stars, light-years. Nothing ever, EVER captured my imagination more as a young child than the mind-boggling vastness of space, the concept of infinity, black holes (WTF?!), the possibilty of other life-forms somewhere out there, maybe even intelligent ones (oh, the daydreams!), desperately wanting to experience weightlessness and wash down floating M&M's with floating, semispherical kool-aid... Not to mention that it's an excellent way to spend time with your little crew
(A telescope capable of seeing a bit of detail on Jupiter is nice too and $200. you can see big photos with great detail all day on TV and it doesn't AT ALL hold a candle to seeing lines on a pinhead-sized circle through a telescope with your own eyes. Not. At. All.)
Also I'd keep an eye on the Maker community. Hands-on is where it's at for younguns IMO.
(Blowin' stuff up never hurt either, if you're safe about it
Good luck!
Life would be so much easier if we could just look at the source code. -- Dave Olson