Last season I used the Camco ceramic filter, just screws inline with the hose:
http://www.amazon.com/Camco-40651-Ce...5794260&sr=8-1
Worked well, water was great. However, it took forever to fill the water tank by the end of the season, because as the filter is used, the flow diminishes, regardless of how well I tried to keep it clean. That's it's purpose, naturally. I got a replacement filter for this season, but I am going to try to only use it if I have a water hookup. For the tank, I think I may try using a filtration pitcher instead, so that the time at the fill station is minimized. Seeing as my tank refills were never filtered anyway, I don't think it'll be an issue for us.
For you, it seems that if you are at a hook-up, putting something in-line (an RV filter) would work fine. If you're using the on-board pump and tank for pressure, I'm not sure how the filter will affect that, based on my experience over time.
FWIW, I do recall some in-line hose-mounted RV filters that had in/out ports that seem like they might work better for you than the one I use (i.e. both in/out in top pointing "up" rather than mine which are at opposite ends). Google is your friend, here