Here is another way to think about it. Yes, that printer is amazingly accurate. But, 2kg of material costs between $450 and $810. Assuming the volume of material to print one of those wheels is pretty consistent whether you get ABS on a roll like most of us do or in a cartridge for the Objet. I'm not sure that their "cartridge" is nothing more than a roll of filament in a fancy plug and play casing. But, with 2kg of 3mm ABS filament, you could print several hundred of your tires for about $40. If you were to get a kit and help the kids build a reprap printer, that can cost as little at $600. So, for the price of one "cartridge" you can build a printer that will teach the kids a whole lot more about the technology than to have them just learn to push buttons on a magic box. Plus, once you run out of filament a few months down the road or want a new color, you are going to have to throw upwards of $600 at it with the Objet. With a reprap printer you can buy all kinds of colors and types of filament from $25 to $50. You can play with nylon, PLA, ABS, PET, wood-like filaments and flexible filaments. Right there you'd spend $4,200 to get that range for the Objet as opposed to $240.

You might want to take it if it's free but I'd build one first and teach the kids the theory. You can learn and waste inexpensive plastic on it until you get good at it. Then, maybe plug in that fancy Objet and have a go at it. And, when the budget is tight, you always have an economical printer to make tires with that will still make fantastic quality parts.