You don't include if you live near them or not. I think if you live near them give the gifts when you see the children, it gives the chance for the children to sincerely thank you or not. lol they are children after all. They may have a hard concealing disappointment. But also if you are far away could you instead send the gift though a service that provides a receipt or confirmation that package arrived? Maybe the parents are very busy and stressed. Especially if the gift for the kids involves any unboxing and putting together. The kids may so excited and they may need their parents help with this part, and the parents might be so busy with so many things that they honestly forgot the send you a text. And or the parents are embarrassed they didn't send the text later and afraid to contact you weeks after the fact.