I don;t think it will be possible to properly use a single Lightboost capable display with two older models that don't support Lightboost, the reason for that is that the glasses also sync differently when being used with a Lightboost 3D display as compared to when used with a non 3D Lightbost model. Still I need to try this and see how it will work out...

As for the newer glasses, they have slightly bigger lenses, so this allows more light to pass, however the visual difference is so minor that you may not notice it at all...