So, a couple of clarifications. You DO want to go with SWM. It can have as many outputs as you want (up to 8) so your current RV wiring will work just fine. If you go with one receiver like the HR21 you will be able to watch one channel and record another (with only the one existing coax wire run) but those TV's must be watching the same programming. The one TV connected via HDMI will be in HD and the other will have to suffer with SD if a coax run or analog HD if using a Component cable run to that TV.
If you don't mind paying the extra $7/month you could put a 2nd receiver in the bedroom and each TV could watch whatever programming. If you will be using the RV long term then I would highly recommend the Genie (HR44 mentioned above) and a client receiver. Watch/record 5 channels and each TV watching anything at anytime. SWEET!