True, any of the ferry rides can be awesome and very fun for ordinary travel around down/midtown and Brooklyn. Also! PS 1 is a modern art gallery in Queens and there's the MOMA Archives not far from there! Plus the Louis Armstrong house in Corona that is cool if music is also an interest. I also recommend Socrates Sculpture Park's Movie Nights, or a Rooftop Film on many nights. Both programs have websites to check out.
I encourage them to buy raw food from a trusted place! Trust me, there are many shady spaces in Manhattan that operate sub-standard and find loopholes to get around it. With the said, Quintessence is awesome and Pure Food and Wine is top notch (and priced as such) but they both fall in that price point. The Cinnamon Snail truck is a MUST! They're number one on Yelp, so they're more than just vegan food tourism, they're pretty big all around.
ETA: oooh also, there's a new raw vegan chain place opening up in Soho and depending on when they come, that might be a good place to stop as well! I think if they happen to take the 6 train all the way to its end past Brooklyn Bridge, it loops around where theold City Hall
stop used to be.