The Expanding Children's Early Learning (ExCEL) Network brought together practitioners, policymakers, and researchers with the aim of connecting theories about the promise of summer programs preceding kindergarten, existing research about features of effective summer programs for school-age children, and the day-to-day realities of implementing these programs for rising kindergarten students. This brief summarizes lessons learned about three implementation issues -- recruitment, attendance, and family involvement -- that affect all summer programs but may pose unique challenges and opportunities for programs for rising kindergartners. (author abstract)