Having to drop out of my sister's wedding

My sister is having a child free wedding and that's fine, that's her choice. She doesn't want anyone under 18 there. Her wedding is next week. My son was supposed to go with his dad's. Well his dad died yesterday. He was involved in a brutal car accident. My sister sends her condolences but she's not willing to change her no kids rule. I don't feel comfortable leaving my son alone after he just lost his dad. My sister said he's 14 and can be home for 2 days and me missing the wedding won't bring his dad back. But I think it's so insensitive to leave him next week alone while he's grieving. I am a bridesmaid but at the same time we clearly didn't expect his dad to die. If he can't come to the wedding I don't want to leave him alone.