I'd recommend it. It's useful if nothing else for the stuff on dilution, cocktail balancing (acid/abv/sugar percentages), and batching. It's helpful even for classic cocktails.

Most of the stuff in it is not dangerous. However unless they're nerdy and willing to spend, they're not going to get much out of the modernist stuff. I'd say bare minimum you need to build a home carbonation rig (~$150ish) or buy an ISI Whip and some CO2/N20 cartridges (similar price all-in) and some Pectinex Ultra-SPL ($15 after shipping) to do anything interesting.