I have girls the same age and our trailer has a very similar bunk configuration. I purchased one of the Stromberg-Carlson ladders and shortened it to fit my bunks exactly (it comes with instructions about how to cut it). It has hooks that hang on the rail, and honestly I haven't had issues with it blocking the path. We just remove it and stash it on the top bunk during the day.
As far as a bed rail, I suggest one of these:
https://www.amazon.com/Stay-Girl-Semicircle-Bumper-Toddler/dp/B00DVI3WXU/ref=sr_1_9_s_it?s=baby-products&ie=UTF8&qid=1495557659&sr=1-9&keywords=toddler+bed+rail
It's kind of a dense foam curb rather than a rail.