For DS, I put an entire outfit (pants, socks, shorts, t-shirt) in a sandwich/ziplock bag then squeezed all the air out of it to be as flat as possible. Then in the morning it was just grab a bag, put on clothes. Ziplock bags are now 8yo and still going strong!
We had a bag for life each with our clothes (so DH was responsible for his own, no 'has anyone seen my...?' crap!) And I had another I'd take to the shower with me, waterproof, could hold everything, kept hairdryer dry, could sit it on the floor.
Washing line and pegs a must, for stringing between trees and drying towels (we'd have shower stuff and pool stuff drying off). You could also do something like bobbing for apples by tying a string around the apple stem and to the washing line: hands behind your back, who ears the apple quickest? Could involve other kids yours make friends with.
Card games: Uno, snap, exploding kittens, virus - whatever floats your boat. Then: that velcro tennis kit, a treasure hunt (internet has huge lists), little notebook if your DC are into writing a diary of what they've done/seen with a little drawing or adding seeds/leaves etc they've found.
A multi socket extension lead, so you can charge a phone and a tablet at the same time you're making a cuppa!
Minimum first aid kit: aspirin, plasters, small tube suncream type thing.
The shoe tidy helsscatspanhle posted is invaluable! You can fill it and still see what's where. Great for charger cables, pens, scissors, some kitchen bits.
We're off camping in July, can't wait!