"It is right and just." Words to live by on a personal level, to be sure. Words that may cause conflict in the business world? It does not have to be that way. I think that the moment the family alerted the management company that the disable veteran needs 48 hours notice to show the house is enough to mandate reasonable accommodations and that should suffice. The request need not be in writing. It can be verbal or written.
The Management Company should inform the Owner of such. In my experience, when those who list homes for sale often ask for little quirks when drafting the listing contract and having 48 hours notice would be seen as that. Does it make it easier to sell or re-rent the house? Maybe. But that is the condition of the contract. Forthy-eight hours notice is not really unreasonable in my opinion.
People decide to move all day long every where in America. As renters, when the contract expires, there is usually a provision spelling out the terms as a holdover which usually involves paying market rent plus a month-to-month fee. If there is no such provision, if I were that family, I would consult with legal aid as to the family's rights of occupancy.
Now, as to the company's right to relet the house: Absolutely, market the house and its expected move in date. Line up Prospective renters for showing appointments but be smart about it. I have rented to people moving cross country into houses and apartments they have NEVER seen because I can show them photos, have a credible listing video to provide, and paint a picture of the property and neighborhood. The Management Company should take the challenge and make every effort to work with that family. Of course, there should be some time line as to when to expect the house to come back, clean and without damage and any other accommodations returned as found at move in, but life is short and in the long journey we travel, the Management Company should give a little.
Just as a morsel of food for thought, I have worked with Residents in difficult times, during job losses, during illnesses, and during the stressful building process. No one's story is exactly the same. But I like to think rational thought and good, clear commmunication results in workable solutions.