We arrived in NY on the Tuesday after Easter in 2010 (early April), the temperature ranged from freezing to nice Spring days. We then went to WDW and the crowds were fine, the weather was great.
This year we arrive in NY on the Wednesday before Easter, we are looking forward to the Easter Bonnet parade on 5th Ave, we have 12 nights in NY before going to Orlando, so I can update you on 'how busy' NY is when we get back.