Just a few comments.
#1 - If the temps are only going to be in the high 20's for 4-5 hours, you should not have freezing pipes. Remember, the water in the pipes are going to hold the temps from the day time temps for a bit as well. So, it will take a few hours for the water to even try to freeze.
#2 - If your site has AC and Water hookup. You can use the "dripping" tap suggestion and some space heaters.
#3 - You should have a blue and red low point drain near your front steps and your FW drain on the other side of the camper. You can drain your lines via these if you are really worried about the lines freezing.
These are just suggestions, so please take what ever steps you feel comfortable with... :-)
2015 XLR Hyperlite 29HFS (installing mods...)
2004 GMC 2500HD 4X4 6.0L