My only additional input is this:
If the camper is going to use a fair amount of power (up to the 15 amp limit of the outlet), the adapter should be as close to the outlet as possible, Trying to suck water through a straw gets harder to do, the longer the straw.
Same with electrons.
Trying to draw more than 10 amps through a long 15 amp extension cord could drop the voltage to dangerous levels. Using an adapter right at the outlet (then a larger sized wire run to the camper) will allow the same amount of amps to flow without the accompanying large voltage drop.
Voltage Drop Calculator
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW