Gradually introduce your dog to the van. Short drives, day trips, just sit or sleep on the drive etc, Don’t force anything, or push too far too soon, try associate the van as a happy, relaxed and safe space. Use the window blinds, I would also try a windbreak and crate training.
When you sit in a van with a dog barking it sounds deafening, when you are 30 foot away in another van, it’s really not that bad. You know your dog and why it barks, so try not to worry what other people think, it’s not a reflection on you.
Then just enjoy your trip as normal, accept the dog might bark a bit, if it does, don’t worry about it.
If you are going to worry about the dog barking or upsetting other campers the dog will pick up on your anxiety and you are setting yourself up to fail.
We go to dog agility shows, there are often hundreds of dogs camping together in a field, it’s very rare to hear any of them bark, especially during the night.