Fleet wood
Where you are camping is there a 50 amp connection also or just a 30 amp & 15 / 20 amp receptical. If you have access to a 50 amp, you could make a box to convert that 50 amp to a useable two 120 volt recepticals. You also could convert your present supply from a 30 amp to a 50 amp supply. Then you could add the cheap heat system and heat your camper with no problems. I have also been using the cheap heat system in my 36 foot Moblie Suite, 2004 model going on five years also. This system cost me $658.00 total.
I also used three portable heaters and a light bulb in the basement. I got tired of tripping over them and when my grandchild tipped one over and I burn't my hands from panicking & picking it up. I'm also a vol.fireman in my home town and during the winter we repond to at lease one home fire caused by these portable heaters. If I was in your shoes I would upgrade my electrical service cord to a 50 amp and install the cheap heat system. This system is something any DIY can handle.
As for Pianotuna if I read his post correctly he is using one 30 amp shore power and two 15 / 20 amp extension cords at the same time. Why!!!
I'm very happy with the cheap heat system and love the even heat, it also keeps my underbelly heated at the same time. Good luck with your future heating options.