By the way, I can give you a few pointers. Those who have met my kids will tell you they are reasonably ;) healthy kids.
My kids are ages 7, 4 and 3 now. And obviously at this age they can eat on their own. Pizza and fries aside, the way we do it is to get some nice healthy foods (like fruit chat, cookies, and other finger food) and place them in easy reach for the kids so they can eat chaltay phirtay around the house.
The eldest gave up milk when she weaned off the bottle. For several years she refused to drink milk. So instead of forcing her to drink milk, we turned to alternatives. Like cheese slices, lassi, macaroni and cheese. Even cheese pizza. These are as good as milk. Then we got her excited about drinking with a straw in a glass, and now she, masha allah, drinks flavored milk (with rooh afza) twice a day, khud maang ke aur shauq say.
The youngest is a bit picky on what she wants, but at her age, we tell her to "try" new things, and more often then not, she does get hooked up. So now at dinner table the kids love to eat desi khanay, like qorma, pulao, roti, vegetables and others. They have begun to show appetite for spices too. Previously we will make two versions of each salan, one with less spices for kids, and one normal. But now the kids just wanna eat regular spices, so its more convenient now.
The thing to remember is at their young age, the kids can not go on a bhook hartaal... so they gotta eat something. If you don't wanna give them unhealthy food, then just prepare the food you want them to eat and place it at easy reach for them. When they get hungry they will munch it down. It also helps if you make them run, play and generally exhaust themselves. That opens up their appetite big time. After two hours of play outside, my kids will generally eat anything in sight. This also helps them to sleep better, after all the excitement and thakann. Do make an effort to cut down on unhealthy food like candies and sodas. They ruin their teeth very quickly.
As long as the kids' weight is within the normal range for their age, there is actually nothing to worry about, even if you think they are not eating properly. If all else fails, talk to your doctor. There are some medicines which increase appetite.