I highly recommend Swarm Commander spray, but get the real stuff from Soods Bee Company. It sounds unnatural but it's made of lemongrass oil and natural queen pheromones. If you can't get it I recommend lemongrass oil, not lemon balm. A very small amount will do.
I think you
should try to get your hive up as soon as you can. It will increase your overall likelihood of getting a swarm before season's end. As Mike mentioned you may have to
feed a swarm later on. Even if a swarm perishes it's not a waste because they will have built out comb for next year's bees.