What part of Brooklyn? Park Slope?

I miss it sometimes - it was my first neighborhood in New York, then I eventually ended up nearby in Windsor Terrace.

Generator hooked into the house panel and water storage are both great ideas for long-term problems. Sounds like you've already got the food idea worked out. One thing I found out the hard way was that when it comes to a lot of foods, my kids are much pickier than I am. Therefore, my expanded food pantry/storage has a lot of what ends up being comfort food for them. Less tuna, more spaghettios with meatballs, the soup is almost exclusively chicken noodle, canned stew is OK but canned chicken and dumplings is not...etc. A lot of trial and error has shown me that we'll be eating a narrow menu if we have to dip into our stores.

As far as getting out of Manhattan, I have to say that the folding bikes was one of the first things I thought of, but a beater bike is also a great idea - IF you have somewhere at work you can keep them. A daypack ready to go that you can slide into an empty deep desk drawer or bottom filing cabinet drawer would be a good idea, too. Something along the lines of the much-discussed "get home bag" for both you and your wife. High on the list for the bag (and for your EDC) should be a flashlight or two. In the blackout, I was stuck on the F at Smith and 9th - luckily outside in the sunshine rather than in the middle of a tunnel or while under the river. By the time we got back onto the platform and ready to go down, the entire interior of the station was pitch black - no emergency lights or anything. Only a very small handful of people (that I saw) had flashlights of any kind. Imagine being in the tunnel with a packed train and then trying to get out in pitch black.

Another helpful item was a regular, cheap AM/FM radio with earbuds. The power went out, the train stopped, the conductor had no info for us for 20 minutes or so, but switching through the stations to WNYC (1010 WINS was down) they eventually developed the story about the scope of the blackout and that there wouldn't be another train (some people were going to stay before word got passed to them).

Sounds like you're on track to have contingencies for contacting/meeting up with your wife to get home together. As far as communicating with the au pair, it's probably a good idea to follow Wildman's suggestion - have a resource for her to know to open should things go bad, so she doesn't have to guess or remember what you want her to do to take care of the kids. Also, as far as communicating with her, I'd think HAM would be a fantastic way to get ahold of her in almost any conditions, but I would guess it's fairly unlikely that you'll be getting her up to speed on that ("what kind of a job IS this?" she'll be asking herself). What might work better is out-of-town/out-of-state contacts. Again in the blackout, most cell phone providers were out (I believe people with Sprint were making calls on the subway when everyone else was getting nothing). It probably took about an hour/hour and a half before I could get ahold of anyone, and that was my parents in Ohio and my in-laws in Buffalo. As suggested, a combination of landline and/or cell texting might work to get the word to a distant contact who can pass word on to the au pair.

Finally, for bugout preps, I've never seen a single source to match this guy's Web site:
http://www.theplacewithnoname.com/blogs/klessons/p/0004.html

A real nuts and bolts, step by step dissection of what to do - pick and choose from his suggestions as fits your needs, but it's really well-organized.

Good luck in the preps.

Dave