With friends that I know will be overwhelmed with Thank you writing.   I will include:  a preaddressed stamped envelope with  a thank you note that fits in the envelope.  All they have to do is sign it.  I tried the no thank you needed but still get one.    One friend told me that she was left with all the thank you notes after the death of her father.   No siblings,  kids or grandkids offered to help.   ( HOW TERRIBLE).   When her mom died a few months later she said it was very thoughtful.