What is a strong legal argument is that it is in the "best interest of the children" to foster healthy bonds with both parents, and promote effective (nonconfrontational) co-parenting.
When one focusses on the "best interest of the children" from that definition, one can then arrive at viable legal options - rather than browbeat OP for a statement another poster made. The OP realizes that the primary risk is grandma, who OP lives with, and wonders if the only option is to forgo parenting time. The answer to that is yes, altering parenting time to minimize illness is a reasonable option, and increasing virtual parenting time could help.
OP also expressed concern that the mom is trying to provoke a confrontation in order to diminish OP's allegations of spousal abuse. Again, I suggested that there are legal ways of addressing that.
Tell me, what legal options have you suggested? Hint: you haven't.