What's the simplest way to transition the family to eating clean?

My kids and I have some skin auto-immune conditions and I really want to try eating clean as our new Year's resolution. I can use all the help with ideas for transitioning the kids with kids-loved ideas, with best places to buy grass-fed organic beef and chicken in the Raleigh area, etc. Should we go "cold turkey" or try one or two changes/replacements at a time. I welcome all the tips you can provide from personal experience.