It is really important to read the labels. It will take a little extra time in the store (I know it's hard with little ones, but worth it.) A couple of things to think about when purchasing food. Try to avoid anything that has trans-fats (you probably knew that already), partially hydrogenated fat (essentially does the same thing as trans fat) and high fructose corn syrup (HFCS). You'd be surprised at how much stuff has HFCS in it. When my daughter was sick to her stomach, I was looking for some crackers and they almost all had it in it. HFCS inhibits leptin which is a protein that tells your body that you are full. So essentially, HFCS tells you to keep eating, it takes a lot to feel full and never really feel satisfied.
Kashi: I try to stick with Kashi crackers and cereal. They make a Heart to Heart cereal that looks like cheerios with hearts in it. It might be a little challenging to eat for little ones though because they are a little bigger and crunchier.
Annie's Homegrown:I've bought their mac and cheese, cheddar bunnies (like goldfish), graham bunnies
Quaker Simple Harvest: They have a granola bar with dark chocolate bits in it that my daughter loves as much as the other kind with all the bad stuff.
Pasta: try to stick with the whole grain stuff. I buy Barilla Plus that adds protein and flaxseed, which is an excellent source of Omega 3 fatty acids...very important for brain development.
Bread: Notorious for containing HFCS, even the supposed "good" kind. I buy Pepperidge Farm Honey Flax.
Vitamins: I try really hard to find the kind that are made from fruit and veggie extracts, most are not. Publix carries a brand called "Berry Garden Gummies". They are shaped like gummy bears. The child has to be at least 2 to take these, though.
Finally, check out http://www.savingdinner.com She is a Certified Nutrition Consultant. I'm not at all creative in the kitchen, but I can generally follow a recipe. She has tons of great, healthy food. She even has ways for you to make up lots of meals and store them in the freezer, like those new chains popping up all over the place. She includes shopping lists and makes it as easy as possible for you.
I'm not a nutritionist, but I teach a college level Nutrition Course. These are some great pointers I have learned. I have a 3 year old daughter and I struggle to make great choices for her too. She is very picky! The only veggies she eats are carrots and lima beans! She refuses to eat just about any fruit, I can still get her to eat baby food fruit, but that's about it.