Depending on the time of year during winter, you may have to play it safe and winterize. I know you are well set up for shorter periods of winter camping, but a frozen pipeline due too extreme cold and a electrical problem can be a game ender? Will you have a place to go to thaw out the RV?
Antifreeze can be added to the holding-tank to keep from freezing without wasting too much energy to heat the tanks.
I would locate either campgrounds open with out-houses and possible electric sites. Get a plastic sink pan to fit in the sink for dishes, etc. Dump the water outside to minimize grey-water going to holding tank. Do #1 & #2 mainly in the out-houses. Doing #1 in the RV toilet only when absolutely limited can go along way on this holding tank.
Be aware of where fast-food restaurants, gas stations, are located for bathroom use. I have gotten fresh-water container filled at these locations. Your customers might help you out here. Some truck-stops, small town waste plants have year round open dump-stations.
If you know the area you plan to work in you might collect this information on the internet before heading out.
Mark B.