We are a family of 8 among of which I have 5 juniors at a growing age with high food consumption. Thus, the need to exchange have we have, water, for the much needed food.
Oh i am sorry to say we have a large family as well with growing children and a breastfeeding mom. We will have to work out the food situation. 
How about I include some firewood? Remember you have the basic food in your arsenal. I would just like to exchange for the extra you have.
Yes i know, as you should take that into consideration as well. You said you dont need water so lets agree on me having 3 and you can have all the firewood. 
Not even to spare a package of food? ☹️
No i think i can take 2 food, 3 water, 0 firewood. 
Food is my most essential as well. A package is not enough for us
As i said we are a family of the same size. I can give you 2 but thats it, in exchange i would like 2 fire wood as we will need to hunt. So you get 2 food, 0 water, 1 firewood
Lets make it 2 food, 1 water, 1 firewood
Sure that sounds fair
ok