Our family took in this bike tour (2 preteens, 1 teenager) during a trip to the Big Island. We all enjoyed the sights, but my wife and I left with the feeling that it simply wasn't value for the amount of money put out for this tour. The guides (Pretty -- knew lots about the local customs and history, and Meghan -- a trained geologist with extensive background in rock formations, volcano effects, etc) were really great, and the group we ended up cycling with bonded really well. The biking itself was disappointing for my wife and I (both love cycling) as it was mostly coasting downhill on roads from parking lot to lot, but our youngest two children loved it (not too much work :)). The sights of the park are really quite worth seeing. I understand running these tours are expensive (a driver, a guide, van, bikes, food, park entrance, insurance, etc) and I'm not sure one could run it on a cheaper budget. However, when we compared the experience of the park by foot (all the sights could be taken in easily and one would get a lot more exercise), or other island experiences (e.g. we could have rented bikes for our family for 3.5 days from BikeWorks, at least 3 nice dinners out for our family, or even a nice mountain bike purchase for a child), we were left with a bit of a sick feeling about the money we had put out for the trip. I would not recommend this to a couple/ family looking for a "ride" that requires much effort. It is more appropriate for someone looking for a stroll and tour that doesn't usually bike much.
Specifically, there was no family or student discounts offered. Children that are between 4ft3in and 4ft10in are difficult to accommodate -- they are too big for the Trail-a-bikes and too small for the smallest bike they have available (Adult XS). The guides were very accommodating and we were able to rig the smallest bike to fit our youngest, but it was a bit dicey at the beginning.