I'm happy these guests found the place spacious an enjoyable for their large family to gather and spend Christmas. That they found three of the five showers too small, the furniture out dated, and the cleanliness not up to their standards, this is something I will respond to below.
The three showers mentioned: These are Neo-corner showers approved by the building and safety code of the county. The height of the shower pipe coming out of the wall is 6 foot 8 inches. It is connected to an adjustable folding arm that holds the cradle for the telephone handle type shower head. This allows for it to be lowered or raised depending on the height of the person in the shower. It is obvious that the guest did not try to adjust it higher. I don't see the height of the shower head as the problem. The problem is the width of the person using it. True, It won't be a comfortable shower stall for an obese person. But fortunately we built in a handicap/wheelchair accessible bathroom that will accommodate any size person.
As for the furniture being "a bit outdated": We have found over the 6 years of furnishing the place that it is best to focus on comport and durability over style. What a guest might consider "up to date" furnishing in their home is not necessarily what is appropriate for a rental place where hundreds of people pass through each year.
And, as for cleanliness not meeting this guests standards: My wife and I were there the day these guests arrived, along with the professional cleaning company that we pay to clean after each guest. We worked for 4 hours to get the place ready to professional cleaning standards and are surprised about this claim.
For these guests who could not fit in three of the code approved showers, who did not find our furniture to fit their taste, and who did not find our cleaning up to their standards, all I can suggest is that they look for another place that better suits them.