Best trick - don't bring things that need to be kept cold.
This.
My family's typical camping fare (adapted from backpacking habits):
Breakfast: hot cereal (sometimes instant); tea&coffee; cookies; hard cheese (not refrigerated); salame/sausages
Lunch: ramen or other instant soup if we're at camp or a picnic area. Trail mix, dried fruit, nuts, crackers/crispbread (Wasa), salame, cheese, etc if on the trail. Apples or clementines.
Dinner: Pasta, rice, or mashed potatoes from a box (we usually come back hungry so we never baked potatoes on the fire, although one easily could!); dehydrated soup (Bear Valley (?) makes a damn good chicken noodle); canned vegetables (peas, corn); canned fish or SPAM tastes good on pasta or rice after a long day of outdoors! Sometimes on short trips we'd be fancy and grill out--you can bring marinated meat just fine, or pick it up at a local grocery in some places. At the beginning of the trip we'd also have some fresh veggies. Cucumbers, tomatoes, and peppers do just fine unrefrigerated for a few days, but may not like bumping around.
Secrets:
-Dried milk. Look in the Mexican food aisle. Not good enough for drinking, but great in oatmeal. Get whole milk.
-Butter. My mom would melt down and re-solidify butter (Is this clarifying?) and we'd take it backpacking for multiple days. No one ever died. Also good in oatmeal.
-Everything tastes better outdoors and when you're hungry. One roadtrip we were down to a head of cabbage in terms of car snacks and in the middle of nowhere (no gas stations, restaurants, etc for hours). Best cabbage I've ever had.
-Gatorade (powdered) is a nice change from water sometimes. Also covers less-than-optimal taste. You can make it at half-strength. Water from campground taps may be pretty cold.
-Freezing water bottles as someone mentioned. Then your ice doubles as nice cool water when you're done! Stress the importance of not opening the cooler. And you don't need cold beers/sodas every night you're camping. Rough it!