So at their age, the problem is that they can't be maneuvering 5 gal vessels for racking, cleaning, etc?
Put a plastic primary vessel somewhere elevated, then rack into 2 x 2.5 gallon (10 litre) basket-covered demijohns for secondary. Those basket demijohns are nice because they have 2 handles - 2 people can easily carry one of them. They are also a lot easier to clean / sanitise because 2 people can hold it in the air and shake it, then turn it upside down to empty it.
After recently purchasing a 20 litre basket demijohn, I don't think I'll use my 5 gallon glass water-bottle carboy for anything other than Apfelwein which only goes in and comes out one time. The glass water-bottle carboys are an abomination - difficult to move, difficult to clean and simply dangerous to work with.