One thing you might want to consider is an adapter that has 2 male 30 amp plugs going to one 50 amp female plug that you can then plug in your 50 amp cord. You can purchase these made up, or as I did I just bought the parts and made my own. I did this due to a lot of the state parks we go to for whatever reason have 2 30 amp plugs side by side in their box so you plug in this adapter and you have 50 amp service. If a park only has one 30 amp and one 20 amp plug I have also seen some folks place a adapter plug on one of the 30 amp legs of this type adapter that will allow them to plug into the one 30 amp and 20 amp plugs, not sure if that's the safest way to go but I guess it works.
Good Luck,
Ron