I'm not an expert but I think the temps "dropping" into the high 20's for a few hours at night will not affect anything...by the time it gets cold it will already start warming up. I think it would take several hours of temps below 30 for anything to freeze...especially inside of pipes and insulation. JMHO I would not worry.
Jim & Linda Tator
2013 Crusier CF34SS GMC 3500 8.1L Dually
154 nights in 2013 - 4,370 miles
178 nights in 2014 - 5,082 miles
365 nights in 2015 - 6,040 miles