What you have is a problem, He has two choices, You can get an HDMI splitter and run HDMI cables to everything or...
You can get an HDMI modulator, basically this is a ATSC TV station in a very small box, you feed it HDMI and it sends it out as a TV signal (RF) to the remote sets.
Your RV likely has a DVD player in it, this outputs A/V only (no RF) but there is a similar box for it.. NOTE: if the Receiver has A/V out it can use that same modulator with a loss of signal quality.
My Dish VIP-211K has all 3 (HDMI, Coax, A/V) what it does not have is authorization (I do not like paying for sat TV less I need to). Will authorize if and when I need to.
Last time I googled HDMI modulators... I was very glad I was not buying one.