Wow-- thanks for all the suggestions. I've been thinking about this, I thought about attractions and other places I've travelled, to figure out where I'm 'lacking', and what I can only do in New York. I came down to this:
Statue of Liberty.
MOMA-- that was on my short list of "I don't want to miss it".
Top of the Rock-- I can get online tickets for an mid-evening time.
Nintendo store-- DS will like that! DH was on the microchip develop/design team for the PS3 and XBOX, so he'll like it too.
At DS's request, we're also going to either the Wax Museum or M&M world.
TALAS (for bookbinding supplies)-- I order so much from them online so it will be fun to actually visit the shop.
I love that there are so many options for each of us.
I think that still leaves some blocks of time to add other things- Central Park, maybe?
Gyros for supper one night.
Either some Japanese food or something Russian or similar. I may come up with a few ideas but see what pans out with other colleagues. An old adventurous-foodie-coworker will be at the same conference and I want to keep my options open in case I can join him for dinner.
The helicopter ride is a great idea and I'd probably do it if it weren't for a bad helicopter-incident in my past...
So, what we can't fit in:
Coney Island -- I felt like I couldn't carve out a big enough block of time for it)
Stock Exchange -- DH and DS don't care, but I'd love to take the tour
Broadway show -- I don't feel too bad about it though because DH and DS have no interest in it, and my mom and I fly to Chicago for a day every year and we often see something at the Oriental Theater. I'm happy to keep my live theater experiences over there with her.
But so many museums! I could spend two weeks going to all kinds of specialty museums: Sony Technology Lab, Math Museum, American Finance Museum, Fire & Police Museums, Micro Museum, Biblical Art, Sea Air and Space, Science Museum, Museum of the Moving Image, Design Museum, I think I heard that a Tesla Museum is in the works... there's even a Scrabble Museum!
Oh, well, now I have some ideas for next time.