Like Gus says, cleaning up an antique is a no-no, with some exceptions. Sometimes fully restoring something like an old toy car, or a real one, increases its value and its attraction to a buyer. I would do a lot of research before I'd do it though, but if they were fully restored, like new wood and they looked like they did when they were new, you might have a chance to sell them to a RR museum, but it might not be worth the cost. Put $100 and many hours into restoration for each one, and they might only be worth $100 each and you've done all that work for nothing. Leave them the way they are and someone might give you $50 apiece.
Don't take these numbers as fact, they are just an example and may not be even close to what they're actually worth.