Glad you're going for it - we took DS to NY for a wedding when he was 4 months and it was a dream. He actually slept better there than he has before or since . The sling was a godsend - subways are very much not designed for buggies.
A couple of things: if you fly BA, and book a sky cot thingy, don't be fobbed off with a strange bouncing chair type thingy. We got given one on the way out - no way was he going to sleep in that, so he slept on me instead. On the way back, they brought it and I said no thanks and they asked if I'd prefer a bassinet instead - not sure why they didn't offer that first as it was a much better bet.
Also, breastfeeding made life much easier, but I did get a couple of funny comments, which I've never had here, along the lines of "would you be more comfortable doing that in the restroom?". Errr...no. It didn't bother me, but if you're in any way selfconscious you might want to think about a shawl or something.
Also, make sure when you book a room you specify you'll need a travel cot and ask them to make sure the room is big enough - we were fine but our friends got to their room to find a travel cot in its bag and absolutely no floor space to put it up. NY hotel rooms are tiny.
Have fun. I'm really jealous!