Toileting and the overnight stay

I see you have the answer - but I'll add this for others: since we too are Michiganders and often traveled while winterized, we either flushed the toilet with antifreeze; or if the temps were going to be below 20 degrees (um, urine can freeze at 28-degrees), we'd bring along our "Luggable Loo" (basically a 5-gallon bucket with a toilet seat and lid) which was lined with a WAG Bag (heavy plastic bag) and filled with about a lb of kitty litter, and would not put ANY liquid down the toilet or drain until we got to warmer weather. The nice thing about this setup is that you can simply tie off the Wag Bag and toss it in a dumpster.

Even though our 5er had enclosed/heated tanks - the valves and some piping was still exposed below the bottom shroud. We'd rather be safe than risk splitting a dump pipe.