Two Special Needs? Any Ideas

I am working on a store an dhave two special needs:

1. I need to associate each purchase with a person - Everybody who buys from this site, a part of what they purchase, the income will go to help support other people doing relief work. So, if you buy $20, 8% will go to person X.

I would like a way to choose who the 8% goes to support. Make sense? Any ideas?

Can it be a part of the account when they create it? If so, can it be changed? First time I buy, it supports person x, second time it supports person y or who ever I choose. Sort of like a default person, but I can change it.

2. Each product has a different amount or percentage that will go to support these people. So, product x might give back 8%, while product y only gives back 5%.

When they check out I would like to have a box that appears saying "Your Purchase Today will give back X dolalrs".

Again, any ideas?

Both will take custom coding and some DB work to store these values

You might look at the affiliate modules in the downloads section for a lead as to where to begin