Disclaimer: I haven not gone through everything to be able to pinpoint to a particular site to be the best for you and your children, your have resource links, its you to do more effort to pick here and there what can fit your desire and make the best curriculum out of these resource sites. “NAD Curriculum Guides” and “Resources for Children and Families: Adventist Pioneers and Ellen White” seems seems to have arranged things for you but am not saying it is the best. I love the creativity of “Kids Bible” it keeps the child going with real stories and pictures. Click on the tittles to open the site
Resources for Children and Families: Adventist Pioneers and Ellen White
Education and Learning – ABC of True Education