I have 5 in my family also. DH, myself, 15 year old son(BIG kid and BIG eater...plays lots of sports), 13 year old daughter, and 8 year daughter(also very athletic and plays sports). I budget $100 a week for groceries. This budget feeds us every meal, except my son usually eats the school lunch 5x a week. DH eats lunch at home everyday, and myself and 2 daughters brown bag. We eat very few meals away from home.
I use VERY few boxed or convience foods. Mainly because we don't like the stuff and it's not healthy. Probably 25% of our weekly budget goes towards fresh fruits and frozen veggies, whole grains, and lean meats. Basic good food. I don't buy "healthfoods" like tofu, organics, only natural sweeteners etc. I just buy healthy "regular" foods.
In a pinch, I can get my weekly food budget down to between $50 and $75, but the quality of the food goes down too. We end up eating more "rice and pasta" dishes that have been completely stripped of their nutrional value. However, I don't think it's terribble to eat those foods! I'm just thankful that I've worked out a budget that includes better quality and healthy foods for my family
Oh yeah! We usually DO eat meat every night for supper. A family could eat quite a bit cheaper if they chose to eat more vegetarian meals. My meat and potato guys would have a fit if I didn't serve meet everynight though!