Our 1 day ended up being 3 days. Since we were at a hotel in Stamford, CT we found it convenient to take the train in each morning. MOMA (thanks to senorcorazon) was a hit especially the Century of the Child exhibit. We bought the little man a toy taxi (which he broke within 4 hours) from FAO Schwartz and watched the horses in Central Park. We also walked from Central Park down to the Village each day and then back to Grand Central stopping intermittently to check out restaurants and architecture. The high line is awesome and we'll definitely go back each time we visit. Thanks again for all your responses. We had a great time, you're all awesome.