I think finding a good patterned fabric is a great place to start the scheme. Then you should pull out two color ways from the fabric, one will be your neutrals, the other will be the accent. I like to look for the color that offers the biggest pop, something like celery green, chartreuse or turquoise. You'll need to select multiple solids, but they can differ slightly. Try a good solid, linen solid and a weave. Next, as you select you patterns make sure you have a variety of sizes and scales. The patterns don't need to the same, but they do need to make sense next in the same room. Let's look at a couple of great kids bedrooms for inspiration...
Ok next let's talk about furniture. You need to strike a balance between practical and fun. Maybe you have a bed that's going to last the next 10 years, but you have totally funky nightstands...yep I think that's a compromise people. You can play with finishes more in children's bedrooms. Don't be afraid to have the legs of your dresser be fire engine red. You can bring elements like steel in as well. Basically, don't get stuck in the old "espresso is the only finish ever" mindset. Pop some gold in your daughters room, maybe a little black lacquer for your son.
Lastly, always have a fun, even weird, element in the room. Nothing ages a room more than being too
Phot credits: http://www.houseofturquoise.com/2014/04/nest-studio.html, projectnursery.com, http://lucyandcompanyblog.blogspot.com/2014/03/install-of-day.html, http://imgur.com/gallery/pMrLM,