Miss Manners: How do I accept kind comments about my child without bragging?

Dear Miss Manners: When I am given a compliment, I always say “thank you,” but I am not sure how to respond when others say kind things to me about my child. I feel more grateful for kind comments about him than those about me, but it feels odd to treat the compliment as though I can take credit for it by saying “thank you.” Agreement feels like bragging. Help?