It can be harder with kids, especially picky kids, to be sure they are getting what they need to. We've come up with several ways of doing this... peanut butter as a dip for their veggie sticks, with lunch... crackers if they won't eat their sandwich, putting toothpics in grapes and tomatoes so they are fun to eat...
You do have to be careful about protein (they need more as they are growing faster, so 0-2 they need .55 grams per lb of body weight, where an adult is closer to .33 grams per lb of weight), healthy fats, iron, and calcium, possibly B-12 (if vegan). But all those can be attained through a healthy diet, or adding a multivitamin into the day.
By the time you are ready for kids, you will have been at this for a long time, and will be more accustomed to cooking for yourself, meal planning for your health, and getting it all to taste GREAT! You'll have that all down and will naturally do the same things for your children.
It is great to be thinking about it now, but don't set limitations on yourself just yet.
When you have kids to look at and think about, and as they get big enough to show that picky eating side of things, then you'll have things to worry/think about.