Generally it's better not to disturb the optics in a refractor.
Dust on the outside of the objective can be left alone if it doesn't cause reflection or light scatter. If it's bad, then try using a squeeze bulb to waft it off the surface of the lens.
You do not want to remove the lens. It has two different glass elements, with an air space between them. If dust or mold is between these elements, you want professional help.
The mold in the box is a problem. It can get into the microscopic pits in the glass surfaces and is almost impossible to get out. You don't want to store glass elements in the box if it has mold in it. So, for now, wrap the scopes in bubble wrap and store away from the box. If there is a lot of mold, then you need a professional cleaner to advise you on whether it's safe to keep. If it's just a little mildew, then spray on some mildew killer and let the box dry in the sun.
Unitron had cardboard boxes and wooden ones. If these are cardboard and the mold is bad, you may be out of luck. If they are wood, a professioinal cleaner can kill the mold and then after scraping it out a light sanding and a coat of clear polyurethane should fix it up.
Avoid using a liquid cleaner of any sort on the scopes. Those cans of compressed air you see at electronics stores can be a problem, too. Most of them are freon-based or have other liquid propellants. You don't want any of those to land on the optics or, worse, to get between the lens elements.
So, the best approach is a light and careful general dusting, an inspection to see if the glass elements need attention, and getting rid of anything that is mold-infested.
I'm a refractor-monkey, myself, and have seen many of the old Unitron instruments. If these are in good shape other than being a bit dusty, they are quite valuable and you don't want inadvertent damage during cleaning to decrease that.
Feel free to email me any more specific questions. I'd love to help see these are treated well and put back into use! If there is any way you can make photographs of the affected areas, that would help us help you better.