If you're at the new (and very nice) playground/park area on the West Side Highway, in Tribeca, and you're completely overstimulated and annoyed and hot and bothered, just a couple of blocks away, a 5 minute walk, is one of the nicest cafes I've been to in forever. Kaffe 1668. It's dark, it's cool (as in temperature, and in vibe), and the people who work there are friendly. They serve nice coffee, and good food, and they have wine in the evenings. Check it out.
And the park is actually great--there's miniature golf, a great playground, and even volleyball. It's just super crowded on a weekend, so it's good to have an escape to a place that couldn't feel more different.