Narwhal, nuff said

So while working this child wanted to put a heavy object into the cart to help their parent. I said to them to be careful, and the parent said, "oh they can handle it." Welp, they couldn't handle it and the object bonked them on the head, there were tears, I was irked, I knew it was going to happen. Should I have done something more? I probably should have mentioned that I told them that I would put it in the cart for them at the end of the transaction or I would get someone to bring it to their car for them while I rang other people up, but they were like, nah 'tis k.