You can't beat Lego Technics in terms of structural toys. They have, in my opinion, the very best 'complexity of what I can build/how hard they are to use' ratio there is, which seems like exactly what your kids want. My roommate just used them for his final project in a grad-level dynamics course to build one of these (not full-size, of course): http://www.youtube.com/watch?v=par9zbTSN58

Not to mention the fact that the drugs would be much more trustworthy; nobody would risk cutting their product with something harmful if there were a legal paper trail back to their business. The other danger of cutting, even with a harmless substance, is that it's impossible to know the true concentration of the drug when you buy it. This is exceptionally significant when talking about drugs with low dose and high potency, like LSD. If the system were regulated with laws allowing the consumer to inquire exactly what's in the substances they buy, the system would be worlds safer.