Translation:Is she waiting for our boys or for yours?
It's optional, too, but preferred. Most people will repeat it due to rhythm. You see, the stress in "na naše chlapce" normally shifts to the preposition "na", so it flows better when "NA-naše" contrasts with "NA-vaše". However, if someone uses intonation to stress "na-NAŠE-chlapce" (not standard), then they will likely finish with "nebo VAŠE".