Here's what we did when we went to NYC for a week (DH was on business)...
Snack foods for plane ride, Cheerios, fruit, etc.
We ate out a lot, but I made sure to get things she could eat. Green beans, mashed potatoes, peas, etc.
While DH was working Reese and I explored the city. It was great, and she loved it.
We used disposable dipes for the trip, most hotels have a laundry service and will wash for you, or have washers and dryers so you can wash yourself. Either way it costs money, and is a bit of a pain, so we went with 'sposies for a week.
If you're going to NYC there is a drug store on every block (Duane Reade) so if you need anything, you can easily get it.
Bring your sling!!! We did a lot of walking and the streets are so crowded I would've hated pushing her through the crowds in a stroller.
Plus it'd be a big pain on subways and cabs and such.