So the people that told you that they would not move are already not your friendly type of neighbor so you shouldn't care about pi$$ing them off. I don't have the same types around me, but I did have the same issue, except they park in front of my house, and I need the entire width of the street to get backed in. So here is what I did - I went to the houses around me and told them that although I don't mind them parking on the street in front of my house, I need the space when I'm backing my camper in. Now, If I come home with it, and cars are parked in front, I still have to knock on doors, but there is no issue.
In your case, after being told no, I'd simply add in that I'd hate to get the HOA involved as parking in the street isn't allowed, but parking my camper in my driveway for X amount of time is allowed. I can come over and advise you the day before I bring it home - OK? Then give them a have a nice day.
If that doesn't work, call the HOA.
