Pouring of rv pad

I assume that you are pouring the slab to be level, or with a very slight slope for drainage. The gravel and concrete that you are proposing should work fine and, if you do your own work on the coach, it will be much more comfortable to work on with a concrete slab. The concrete will also highlight any leaks or drips that you have that might need attention. I put a steel trowel finish on my slab since I was more concerned about having a very smooth surface rather than a non-skid broom finish. Traction was not a problem for me and the smooth concrete finish is easier to keep clean. Enjoy!