A basket ball court is 94 x 50'. 4,700 sq ft.
The Hilton where my high school had its prom a couple of years ago could muster a room that's 15,200 sq ft. The prom took a space, with performers, places to sit, buffet, and dance floor, much larger than a basketball court. Not the full 15k sq ft, I think.
The current White House ballroom, as good as any in the world, is about 80 by 37'. A bit under 3,000 sq ft. If that graduating high school class held their prom in the White House ballroom, they'd each have a 2 x 2' space to stand i (if they all showed up at once--about 450 showed up, so they'd have a generous 2.5' sq ft space to stand in--eat, dance, whatever. But that's not allocating room for the band, buffet, chairs ...
A sock hop within the white lines that indicate in bounds on a basketball court would not fit within the East Room of the White House.
A tennis court, at 78 x 36' fits in the White House ballroom, with a generous 1' on either end and 6" on a side to spare for the refs and the ball boys (just make sure that they're slight of build).
That's not an argument for building a humongous Trumpian ball room.
But it does put in context exactly how expansive the largest reception area in the White House is. It is not a large space.
= new reply since forum marked as read