True, at a recital I played recently, everything in the last half of the program (which was all 20th Century, not counting the Chopin Prelude I ended with) was what the audience enjoyed, they were bored by the first half (which consisted of Motzart, Bach, and the like).
So I say throw in the last movement from the Ginastera Piano Sonata, the Roman Sketches, maybe the Gershwin Preludes, Or some Debussy. (people always enjoy programmatic stuff like The Engulfed Cathedral, since it gives them something to latch onto while they listen)