is president's day in washington dc going to be super crowded?

[Schmoe]

my husband booked a vacation for washington dc over president's day because here in ontario it's family day and he thought 'well, since they don't have family day in the US, it won't be too crowded but i won't have to take a day off work' not realizing that the same day is president's day in the US. *sigh*

is it going to be super busy or crowded that day at all the museums and other attractions there?

thanks.