Read the reviews before booking, they provide valuable information that will make your stay very enjoyable
1) If you take the wildlands express shuttle in (airport shuttle), they drop you off 3 miles before the campground, and you have to hike down a rocky road which can be tough with lots of baggage.
2) We managed to save money (20 per person) to take the shuttle above and hike down, but I 100% would not recommend booking the shuttle both ways. I would recommend booking the transportation that the campground offers at their website. This is either a land or ferry transport (up to campground to decide day of)
3) Know that many past reviews mentioned the campground being empty during their stay, we stayed in early June 2021 and it seemed to be the weekend of their first large group of kids - this definitely impacted the quietness of the experience. I would ask in advance if the time you are there is mostly occupied by other Airbnb'ers or if they have a large group coming in.
4) Bring your own food to cook, from the Vons in Avalon, there is a large industrial fridge storage for you to store food. The campground offers some options but if you want fresh food, bring your own and a camp stove and cook. We would have booked the transportation via the campground into the camp if we had more food to cook.
5) Bring sheets and sleeping bags, it gets very cold (at least in May) at night.
6) Bring expectations of a remote island campground, but don't have high expectations for fancy accommodation, this is a campground, not a hotel.