Spare socks. Lots of spare socks!
Pack of cards - regardless of any other games you bring, always bring a pack of cards as lots you can do with them.
Think through what you will want to eat and drink (and how you can cook). Easy meals, preferably ones that only need 1 pot if any cooking required. Can you pre-cook a meal for 1st night so you are just reheating it? Perhaps a rotisserie chicken, crunchy french stick and some salad bought en route to the pod from an outing as another evening meal. Wine in a box/pouch is useful rather than a bottle. Sachets of hot choc (can add boiling water and cool down with milk). Maybe make up the dry ingredients for pancakes in a ziploc bag or a clean plastic milk bottle, to add milk to when away and shake up for a fun breakfast one morning. And snacks- you will be hungry in the fresh air. With Cub Scouts, I put out a bowl of fruit cut into portions for when they come back from activities, and jugs of squash made up to pour out (or fill water bottles when smaller groups). On family camping, there is usually a fair amount of crisps while dinner is cooking, or things like carrot sticks and a tub of hummus.
Spare shoes is good - as someone else mentioned, something like crocs or flipflops that can get wet, or wellies to walk across wet grass.
I have a policy of putting one complete change of clothes, from the skin out, and including a pair of shoes, in the footwell of the passenger side of my car - it doesn't come out on camp, but is there and easily accessible at the end if weather has been awful and I am soaked/filthy at the point of driving home, so i can change if need be. (I learned after an awful camp and dreadful pack up on Cub camp 1 year when I had to drive home absolutely exhausted, totally soaked and covered in mud - and it took a full service valet for my car to recover, let alone me! and it has been useful on a number of other trips since!).