A general word of advice on sightseeing in New York.
Tourists often spend their entire vacation in New York standing in line (or as New Yorkers say, “on line”). This is often unnecessary; there are usually alternatives.
For example, one can choose to avoid the Empire State Building during the day (it is open, and much quieter, late, until 2AM), skip the Statue of Liberty in favor of the Staten Island Ferry, and stay away from the Guggenheim on Monday (it is one of the only museums open that day).
Also, there is no reason to stand in line for a Broadway show if you already have a ticket with an assigned seat. If you prefer, get a drink nearby and come back closer to curtain time, when you can walk right in.
The lines for bus tours can be absurd because tourists all seem to have exactly the same itinerary – which is get on a bus in the morning in Times Square, get off for the Statue of Liberty, and finish on the East Side in the afternoon.
Why not go downtown in the morning, and save Midtown for the afternoon? You will thank yourself for avoiding the crowds.
Also, understand that buses are the slowest way to go crosstown in Midtown Manhattan during peak hours, and taxis are not much better. You are often better off on foot. Additionally, New York rush hour (especially in Manhattan) puts much of the city in gridlock – all subway lines and roads will be much busier from 4:30pm to 6:30pm.