Hi,
Drusba covered most of it!! We were there last year the week leading up to Easter. We knew from reading info here and elsewhere that it would be crowded and it certainly was. W/ FP, Ps's, and lots of planning on my part we did everything we wanted to do. Crowds increased all week up to Good Friday (our last day there). I think I was expecting much worse, so I wasn't so disappointed.
The weather last year was beautiful, but it was the end of March -- in the 80s and only a few drops of rain one afternoon.
Whenever you choose, I'm sure you'll have a fantastic time!