My friend, colleague and renowned expert on heritage language learning Prof. Kim Potowski (U of Illinois, Chicago) has co-authored a recently released book:
Beaudrie, Sara, Cynthia Ducar and Kim Potowski. Heritage Language Teaching: Research and Practice.
Although the table of contents doesn't show a separate section on community service learning and heritage speakers, heritage speakers definitely benefit in unique and important ways from CSL courses.
Because Kim knows this, she also invited Prof. Glenn Martínez (the Ohio State University) and me to co-author a chapter in a handbook-in-progress. She is including a chapter on Spanish for the professions and community service learning, and Glenn and I would use this guiding question in our writing: What considerations are necessary when engaging heritage speakers in courses focused on Spanish for the professions and on community service learning?
I hope that you will read and benefit from Kim's newest book as well as the large bibliography she has built over the years.