Zend certified PHP/Magento developer

How to add “child” product based on quantity of “parent” product to customer cart?

I want to create a product consisting of a panel(parent), screws(child), and washers(child).

Each panel requires 25 screws and 25 washers to install, however screws come in boxes of 100 and washers come in boxes of 200 which the customer pays for.

If a customer purchases 1 panel their cart will require 1 box of screws and 1 box of washers. If they purchase 5 panels their cart will require 2 boxes of screws and 1 box of washers. The customer can increment panel quantities by 1.

I imagine I will need an extension to achieve this, perhaps multiple bundle products inside a configurable product, or buy number of x get number of y?

I have tried a configurable product with the options being the quantity of panels but it will end up confusing for the end customer and laborious for me if a customer wants to purchase 100 panels.