Kids 12 and under are not even supposed to take the vaccine. We're looking into options for our grandchildren. Calling different private schools to see if they demand masks. Might end up homeschooling them, if necessary.
https://www.cdc.gov/coronavirus/2019-ncov/community/schools-childcare/k-12-guidance.html
"Masks should be worn indoors by all individuals (age 2 and older) who are not fully vaccinated. Consistent and correct mask use by people who are not fully vaccinated is especially important indoors and in crowded settings, when physical distancing cannot be maintained."
Pray and persevere, find an online homeschool conference and sit with your grandkids' mom's on them, especially the talks for newbies and the uncertain- usually titled something like "You can do this!". There are some great speakers who articulate the reasons and motivations very well.
Also send them links to articles on the HSLDA website.