case of study : sponsorship formular

Hi all,

I have to build a sponsorship formular but i don't know how to do.

There must be the ability to register 4 user at one time, just the main info (first name, last name, email, phone)

Once the formular sent, these informations are to be recorded in the database (may be a custom table named tl_sponsors) , in addition to the currently logged user.

A custom message is also sent to the sponsored person, inviting him or her to register on the website.

I'm using also an isotope built shop
Once the sponsored person registered, if he or she buys an item, then the sponsor receives a 10% off discount

Anybody as a solution for this ?

i am completely overwhelmed :D