You can't force someone to like someone else, even if it's a child or grandchild. Your son has special needs and you understand how to care for him. Your mother does not.

There are two sides here - on the one hand, your son deserves understanding and compassion. On the other hand, older folks like your mother sometimes have a hard time adapting. If she is used to a quiet, orderly environment she may not be able to deal with a special needs child.

I agree with other posters on here that instead of cutting off the relationship altogether, there might be better solutions that don't adversely impact your son.

For example, yes, invite your mother to come visit you for a few days, and offer to put her up in a hotel if she is not able to afford it herself. Or, instead of going to visit her for 2 weeks, only go for a few days. If her other grand children enjoy their relationship with her, send them to visit for a week or two during the summer. While his siblings are gone, participate in special activities with your youngest that make him feel special.

With Covid going on right now, you have time to figure out what works best.