Yes. Thank-you notes often get forgotten, but they still very much serve a purpose, not only in showing guests your appreciation but also in teaching your child the importance of manners. Even if a guest attends without a present, it is important to send a note thanking them for attending your important celebration. Written thank-yous are required if yours was a more formal affair; e-cards may be used for less formal events; and email is better than nothing. If your child is too young to write the thank-yous, you can have them dictate the note or pen it yourself and have him “sign” each one and/or draw a picture of the gift.