If a grandmother has positive reactive igg and negative igm for corona virus and grandchildren are negative for both igg and igm is it safe to visit the grandmother?

Uncertain: We still have a lot to learn about this disease. For instance, a number of people who were positive on nasal swab (PCR), recovered & tested negative, than went on to redevelop disease and were positive again. We still don't know how much immunity develops with antibody production. A child who tests negative, may still become infected. It is a complex issue.