Using Marketpress when 'item' has four different prices dependent on quantity purchaed.

Greetings. Explanation of what I am doing will save much time. I am selling baseball camp subscriptions. The team offers discounts dependent on number of weeks purchased. If parent has two kids, this discount also applies (as in, two kids for a week == two weeks). Client has four different price breaks, so I need to find a way to alter the price per week fee dependent on the number of weeks purchased (avoiding the whole 'how many kids do you have element' and going entirely on quantity).

Yes, I can simply 'ask' the user how many weeks and/or how many kids they have and then provide the appropriate link to the correct pricing, but it seems like there must be a more elegant way to do this.

Any suggestions would be oh-so welcome!