Do I pull him out? Opinions- thoughts?

My sister in law is always starting stuff. It’s like she gets a high out of talking about my kids and husband and me behind my back.

I let my four year old son stay at her house with his 4 year old girl cousin.

My sister in law messaged me, “ummmm, hey (my sons name) tried pulling down (her daughters name) panties and kissing her on the lips”

I know for a fact my son doesn’t talk like that or do stuff like that. That’s exactly how she is. There’s no telling how she treats him when I’m not around.

He won’t be going there anymore.

My husband wanted to take his niece and our son to Chuck E. Cheese but my sil told her husband, “not if that kids is around” my BIL (hubbys brother) isn’t happy about what she said. She’s basically treating my son (who has ADHD and is hyper) like a rapist

She’s literally telling all her family members and my husband what my son allegedly did. I honestly feel like she is toxic and won’t be going around her anymore

My son got approved for head-start and might be in class with his cousin. Do I pull him out?