Have you asked those operators how the long the runway needs to be for their operations? If not, that would be a very good starting point. Other than that, maybe if you can tell us the elevation of this aerodrome, we might be able to answer the question, in more specific terms.
Just off the cuff, I'd have to say that, for a sea level aerodrome, the runway length needs to be in the vicinity of at least 1500 to 1700 metres. This length may not be enough for some of those types though, if you want to maximise aircraft load and fuel. To allow for the maximum operational flexibility, those types probably need something more like 2000 - 2200 metres as a minimum, but that's really just a guess until you can give us some specifics.