If I took my dogs to the vet every time someone spit something up, we'd all be living on the street. Predators/scavengers are put together in a way that they eat first and ask questions later (survival mechanism since the kind of food they eat can be stolen by other animals) and barf at the drop of a hat. Mine have a fine disregard for what is actually "edible" vs what "can be swallowed" and things will get spit up.
However.... there's vomiting and there's vomiting. If a dog throws up a meal and re-eats it, or spits something up that never should have been eaten and seems fine, that's one thing. A little bile before breakfast but then eats like a horse.... no problem. But people have to really use their heads. Repeated vomiting, not eating, seeming "off" and other symptoms of stomach distress or illness should be attended to quickly. If I think one is sick, there is zero waiting time before I start considering my options. Listen to your gut.
Keep in mind though, that as scary as this is, this is a very small number of dogs. That's not to say that there isn't some cause for concern, but the odds of any given dog being exposed to this or catching it are still quite small. Don't be driving yourselves crazy. (I know for some of us, that isn't much of a trip, but still.... )