I would vote for Presidents' week. I think it might be easier to manage crowd wise than Easter week. I was there around Presidents' week in 2014. I was there the week leading into the Monday holiday. Things were quiet until the Thursday going into the weekend. It was very crowded in the parks during the weekend. We left on Sunday/Monday, I forget which now and so I cannot say anything about Monday, Presidents' Day itself. But I would expect the weekend will be very heavy crowds and then the may taper off during the actual week following the holiday.