Don, I always like to have a decent amount of bees covering brood, no matter what time of year. I just about always shake at least one full box on site. If you are able to bring them to one of your yards that night, you can simply open the vac boxes. By morning they have left and entered the hive.
Here's a tip for you when shaking them at night: better to be wearing dark colors, white will attract at night.
One of these days I'm going to dye one of my jackets jet black! :-D