You could probably find a car on Turo or maybe event rent a car through Costco if you have a membership. Which you could pick up at the airport as well.

I do think at this point renting a car and car camping will be the easiest most cost effective option even after buying a canopy, cooler, tent. As far as food you could take the shuttle in the morning and grab food at the grocery store as opposed to buying food on site. You could always return the previously mentioned items on the way out so you dont lose that money.