What styles do you guys usually cover? 
Kakariko Prom I think would be good for waltz learners, and maybe 
 
 and Valse Aeris for the more advanced.There's also Moontang for tango but it has a really long intro. 
So does Salsa Snake... 
Stray Donkey Strut for swing, maybe? 
Love Hurts might work as a chacha. Or Smooth As Honey if you want the students to go WTF, haha.