Congrats on your first steps toward change!
This is a tricky one, not because there isn't an answer but because there are SO MANY answers! Everyone's diet is going to be different, yours won't ever look like mine and mine won't ever look like yours... so it's a matter of personal taste and budget as much as anything.
There's no reason to give up your favorites or staples. One of the things I learned is how much you eat can be as important as what you eat.
You can still have shepherd's pie and chicken and potatoes, just practice proper portion control. 3 oz of meat is one serving (without the bones). If you're making baked or mashed potatoes, just watch how much you add for toppings. Can you use a lower fat milk or alternative? Can you be happy with salsa on your baked potato instead of sour cream and bacon bits? What about roasting with a touch of olive oil instead? I love throwing a huge pot of veggies in the oven to roast.
Make a list of what foods you know you and your family like - not just whole dishes but individual ingredients as well. Then work on portions. Large servings (1/2 - 1 cup cooked) of non-starchy veggies like salad greens, asparagus, carrots, peppers, beans, broccoli, etc. Buy frozen vegetables at first if you're worried they'll go bad before you get to them. It's so frustrating to try to eat healthier and then end up throwing good money in the trash because the food went bad in the fridge.
If you fill half your plate with vegetables, then 1/4 with some protein/meat, and 1/4 with a whole grain like brown rice, whole wheat bread, pasta, or similar, that can be a good way to gauge portions, but it's always best to measure instead of trying to eyeball.
You can still enjoy steak, chicken, fish, etc, just be sure to watch how much you eat. Baked is better than fried, grilled is awesome.
For quick meals for breakfast and lunch, my favorite is an egg wrap. Fried or scrambled eggs (or even an omelet) wrapped in a tortilla, pita bread, or similar. Add some fresh spinach leaves if you have them, and maybe a touch of guacamole, salsa, or light mayo (just watch the serving size).
Oatmeal is good, watch the sugar content of most instant, though. Fruit, yogurt, or homemade frozen pancakes/waffles can all be good. Sandwiches or even dinner left-overs can be quick lunches. If you have extra time during part of the week or weekend, you can chop up fresh vegetables to be ready to grab at a moment's notice.
A quick lunch or dinner can be a taco salad, using a hearty lettuce base, add 3 oz of ground beef, chicken, or other protein (I've used refried beans for this, too), then top with taco toppings like onion, tomato, jalapeno, salsa, guacamole, and 1 oz of shredded cheese. Mix it up really well so you won't get to the bottom and have just bland salad.
The best choices will usually be whole foods, but that doesn't mean you can't have treats as well. Just, as in all things, watch your portions.
If you have a crockpot, that's an excellent way to make your own soups, too. Fill it up about 1/2 or more with chopped veggies, add some (low sodium) broth or broth cubes, and water, add a bit more seasoning because those never seem to be quite enough, and then enjoy!
The recipe area of Spark has great ideas for all occasions, food types, and meals.
But when it's all said and done... make small changes you can stick with, and that you and your family can sustain over the long term. There's no point burning yourself out and then deciding it's too hard. Give yourself the time to incorporate little changes for better health.