How would you politely tell your ex’s parents to stop sending you and your kids gifts?

They’ve been a huge part in our lives for 6 years. I love them as much as my own parents. But my ex has moved on and has hurt me so deeply. I’m struggling to cope with it all. But they live 5 hours away so i’ll probably never see them again. They sent us birthday gifts and each one hurt, reminding me of what I’d lost. I don’t want them sending Christmas gifts. But I can’t find the words to say goodbye either. I feel like I should explain as I know my ex won’t have said anything. They still don’t know why he got divorced.