Not wanting to sound smug ...BUT I have access to Dry-Ice all year.
So during the middle of last years heat wave I was lying in my hammock watching a father & son erect their tent in blazing heat... they were very thankful when I took over a few ice lollies for each of them.
The wife and I only go for 3 days at a time and a full cooler worth of Dry-ice lasts just long enough before it gases out
Aside from all the useful replies already given, If you are fortunate enough
to camp beside a river I can heartily recommend putting beer and the foil bags from inside wine and cider boxes in a fishing keep net lowered into the river. ... works a treat
We use something similar to this.
If we're away from the site, wrapping the bottle in kitchen roll and keeping it wet, does the job nicely. (Works on milk too)
------------- Some days you are the dog,
some days you are the tree.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.