I have to think about how to make sure that they do not intersect in the house and on a walk. But I don't have enough rooms to give each of the eighteen dogs a separate one! Luckily, these situations don't happen very often.

Probably it would be a good idea to look for volunteers to take them for a walk/run every day (or at least more often). Of course I do not know how often they walk/run, how many people have regular contact with them, and I also do not know what is their relationships with strangers. But going for walks/runs more often with them is probably a good idea. This is just/only an idea/suggestion.