The foxes won't voluntarily move the kits at this point. They are probably just now old enough to leave the den to learn to hunt with their parents. The kits will disperse in the fall to find their own territories. If the property owners do not want the foxes on the property, they will need to hire a nuisance wildlife control operator (NWCO) to trap and euthanize the foxes. If they just need to get the foxes out from under the deck, the NWCO could trap the foxes and release them elsewhere on that same property. But before the foxes are released, the den would need to be filled in first, and some sort of wire or fencing would need to be installed to keep them from excavating the old den or digging out a new one.