Years ago we had a couple of occasions to set off bug bombs due to the dog picking up fleas. Basically, put away anything we ate off of, covered the counters, table tops, etc. Everyone and the dog out of the house for, I think it was 3 of 4 hours. And set off an aerosol can on each level (basement, 1st floor, 2nd floor), the cans had a lock-on trigger.
It killed everything that creeped or crawled. The house was absolutely bug free for quite some time after that.
Black widow spiders? I'm generally fairly tolerant of nature stuff, but, yeah, you gotta get rid of them.
Just a couple of thoughts. I'd make sure customer's car windows are fully up. Set the bug bombs off well away from the cars. Cover any coffee machines, snack areas, ash trays, etc. to the insecticide doesn't settle on them.