Ask them to go Patrolling with you
From Create Your Own Story
"Tell me why don't we get out of here, I'm bored anyway." To most it would seem like you were referring to an more explicit encounter, but to Wonder Woman and Supergirl it was clear.
"Consider it a date Bruce." Wonder Woman just smile, obviously thrilled
"I'd love too" Kara still seems shy towards you for some reason, but you don't question it
Tell them to meet you at the top of Wayne Tower