At my church, we use a variety of Bible Translations. But I am constantly getting emails from readers who need Sunday School Lesson only in the KJV. One easy solution is to edit our free lessons and simply use the King James Version. Most of the content would only require an easy change of wording and you can have hundreds of free lesson plans using the KJV.
Here are some of the main publishers I know of who are making KJV Sunday School curriculum.
You can get International Sunday School lessons in the KJV translation. That would be an easy way to provide high quality adult Sunday School materials.
Regular Baptist Press is one of the largest KJV publishers out there.
LifeWay still makes some materials available int the King James.
If all else fails, you can go to specialty websites like this one to find all produces in that translation.