SNAP Challenge via The Non-Consumer Advocate

Katy from The Non-Consumer Advocate was featured on a breakfast TV show recently (Sunrise) and since then I have been reading along in earnest.  I am always looking for ways to reduce our usage and wastage.
Katy has proposed this week to be a SNAP (American welfare system food stamps) challenge - basically you need to use a budget of $4 per person, per day for food expenses.  Being American I am not really sure how the cost of living compares to Australia, but seeing as in May last year I undertook a $100 grocery challenge I decided I would try to repeat that again for this week - that sounds fair for a family of 4.
For the purpose of this challenge, I am not using it as a shopping challenge but rather a consumption challenge.  The way I shop is usually based on what is on special - in particular, what is non-perishable.  For example, last week I got 700mL jars of Tomato Passata on special for 99c ea - so I bought a case of 12.  This will likely last us 2 months, but I was able to get it at half the regular price so why wouldn't you stock up while you can?  So for this week, I will be noting what we use and calculating the cost of replacement (or where I know I got it on special, the price I paid for it).  I think this makes the most sense to me - why would I go and buy another bag of flour, butter, oil, spices, etc when I have them all in my pantry/fridge and will only be replacing them when they run out?  There are also things that I only buy on special that I already have on hand - like rice and pasta so I have plentiful stocks of these and will only buy more when they are on special again.
I have drafted my main-meal plan for the week to look something like this:
Monday - Taco Wraps
Tuesday - Fettuccine Carbonara
Wednesday - Asian Chicken Soup
Thursday - Rice Paper Rolls
Friday - Beef Stroganoff
Saturday - Chicken Risotto (+2 extra adults)
Sunday - Pizza (+ 4 extra adults)

Breakfasts are generally either WeetBix or Toast, and lunch is sandwiches or leftovers and a few snacks so they require less planning.

I find that it is best for me to see if any ingredients are on special that week and base my meals around that if possible.  I also consider what I already have or what needs to be used up and add to that to make a meal - for example, I already have the tortillas and taco seasoning, and have lettuce, tomato and avocado that need to be used up so it makes sense to make these into soft tacos as a meal early in the week.
Saturday and Sunday we will be having guests over for dinner so I hope to be able to stretch the budget to include these too.