The RF modulator should work just fine to get a signal to all TV's. It will never be an HD signal so you may be a bit disappointed in how small the picture is on your HD TV and the quality is pretty poor.
All coaches are wired differently so you may have to try running coax to different connections to see if any are common to all TV's. There should be something. Do you have a box somewhere where there are a couple (or several) buttons labeled TV, Cable, Aux or something similar? One or more A/B switches? If so, this is where your satellite TV connection will go but you may need to make some modifications.
Maybe if you give us some details about what kind of RV someone might be able to get you some better answers.