Fruit is ALWAYS good to keep in the house. It's an easy snack that's guilt free.
I like sugar free pudding that comes in the individual snack packs....with a little dollop of low fat whipped cream...cures my chocolate fix. Blue Bunny also makes fat free low cal fudgecicles.
I also keep the vaccuum sealed packs of tuna in the cupboard for a quick lunch when the kids are having something delicious (but off limits)

No draining or mess, and I can add a sprinkle of cheese and a little low fat mayo-good source of protein and not high in calories. Keep it all in the pack and there's not even an extra dish to wash

I also keep thin sliced deli meats to add to a salad for something different for lunch. It keeps me from wanting to throw on a ton of croutons or bacon bits, and it adds protein to the meal without a whole lot of calories. Just be sure to be conscious of dressing-it's easy to add enough to totally defeat the purpose of having a salad instead of a cheeseburger

I actually use a low cal/fat dressing, and when I buy the bottle I pour out about 1/3, replace it with
water, and shake it to remix. Doesn't make a big difference in taste, but cuts way down on the calories and it coats the salad better.
As far as cooking healthier, you really have to just read labels. Instead of pizza- make pizza pasta.....use whole wheat pasta, reduced fat pepperoni and cheese, and some spaghetti sauce-a no fuss casserole that's way healthier than domino's. And everyone will like it, so it's not a "diet" meal you have to make separate for yourself.
Take the things you already like and just try to find a way to make them healthier. You can find a million
recipes for a healthy cauliflower and broccoli salad-but it will do you no good if you would never eat that.
Another go-to meal of mine is mediterranean chicken, because everyone likes it and it's easy to make.
Take boneless skinless chicken breasts, and season with salt, garlic powder and pepper in a baking dish at 350. Pour a can of Italian style diced tomatos over the top and bake until done, about 45 minutes. It keeps the chicken juicy and adds a nice flavor, and for the kids I usually even sprinkle a little cheese on top-and I serve it with pasta tossed in a little olive oil and toasted garlic, or some brown rice cooked in chicken broth instead of water.