I figured I'd move my NYC advice over here as you suggested - I'm totally enjoying helping you plan though!
haha - So Coney Island and Williamsburg are both IN Brookyln! ;) But Brooklyn is a very big place. However, you could definitely spend a morning/day at the beach/Coney Island and then head to Williamsburg in the afternoon/evening (sounds like a great, though probably tiring, day to me) - though you might want to go back to wherever you're staying to get un-beachy, you'd have to decide. The downside of Coney Island is that it takes a long time to get to, but it's definitely worth a visit :) (Williamsburg on the other hand is verrry close to Manhattan by subway - just a a few minutes from union square). P.S. If you guys find yourselves done exploring Coney and just want a beach to hang out on - Brighton Beach (just a few stops back towards Manhattan on the train) is better when it comes to the beach itself in my opinion!
And no, not too cool for you! ;) I'd say the crowds in those places are probably mostly mid-twenties to mid-thirties, perhaps slightly hipster, but hey, it's New York! ;)
Would you believe I've never been to Century 21? However, a good friend of mine also got a beautiful coat there, so I know I need to check it out too.
As far as pizza goes, that's a tough one - everyone you ask will tell you something different! (And even I'm not sure I know where my favorite slice is). However, I think I would probably send you to Joe's (yes that's Joe's as featured in Spiderman 2, haha) on Carmine St. in the West Village (another great area for wandering around/exploring). And it just so happens it's not far from a Joe coffee either! Something about Joes'? haha 1385 days ago