Scaling recipes

I work for a daycare and we need to be able to take recipes that were mainly created to serve adults and scale them down to the required size portions, which vary based on age groups. Ideally, so that we know how much of each ingredient to purchase total. I'm having trouble verbalizing this, but basically we'd be able to enter how much of each ingredient (meat, grain, spice, etc) required by a recipe, enter how many of each type of child being served (Child A group, Child B group, Child C group), then it would calculate the amount of the ingredient needed in a convenient measurement (ounces/ pounds/ etc).

For example, here is the required serving size for each age group of meat:

Standard Serving - Age Requirements table
Age Group Meat (oz) serving
0-5 Months 0
6-11 Months 0.5
1-2 Years 1
3-5 Years 1.5
6-12 Years 2
13+ Years 3.5

So I'd want to be able to put in the number of each group and have it calculate against a recipe.

Total Requirements Table
Age Group No. of children Meat (oz)
0-5 Months 0 0
6-11 Months 0 0
1-2 Years 9 9
3-5 Years 20 30
6-12 Years 5 10
13+ Years 6 21
Total ounces 70[/td]

Any help is appreciated - I'm kind of at a loss as to how to translate the data into what I want to see. New to forums so I apologize if this post doesn't make sense.