If we're going on a day walk (so for 3+ hours) we'll usually bring 2x small backpacks (we've got small Macpac packs, we think they're around 16-20 litres each). We usually wear sneakers or trail runners. We've started buying trail runners for the kids instead of normal sneakers or tramping boots (these are the asics ones we brought for Miss 6). They can wear them as sneakers but they double as tramping boots, we'll probably reevaluate at some stage and look at getting them tramping boots for better ankle support but right now we've found them ideal (their feet grow so fast we like that trail runners are so versatile... it's not so easy to play sport at school in tramping boots :)). We also usually get the kids to layer their clothes so they can add/remove layers as needed. Usually a short t-shirt/long t-shirt and a light jersey. We don't like anything bulky so generally we stick with merino jerseys.
Food & Drink - we take heaps of yummy food.
We usually carry around 3 - 4 liters
We also bring:
If we're going on a "tramp" - basically into the Remutaka Forest Park or Tararua's where we don't have cellphone reception we'll throw in our tramping first aid kit which includes survival blankets etc and let someone know where we're going.