While you don't need to write a thank you note to everyone that attends a funeral, it's appropriate to write one to anybody who went above and beyond for you in a time of grief. Pallbearers, officiants and friends who bring food, send flowers or make a memorial donation to a charity should get a note of gratitude. These notes are short and sweet, and should be written simply from the heart.
When you're addressing funeral thank you cards, it is acceptable to be casual. Since the gifts and sympathy cards are most likely from close friends and family, simply address the note as you would normally address your friend. For example, you may begin with, "Dear Sarah and Mark," or even, "Sara and Mark."
A thank you note doesn't need to be very long. Just one or two sentences is the common etiquette, according to Emily Post. For example, you may say, "On behalf of our entire family, I want to thank you for sending food to the house during such a difficult time. It meant more than we can say to know you were thinking of us."
After you write a few sentences, you can sign off by writing "Love" or "Sincerely," depending on how close you are to the card's recipient. You may either sign with your first name or on behalf of your family, such as "The Smith Family." When in doubt, use the name of the person or family entity that received the gift for which the thank you is written.
A thank you note should be handwritten, as opposed to using a pre-printed card and simply signing it. If the person who received the gifts and cards is not able to write the thank you note, it's acceptable for someone else in the family to take on the task. You should write something like, "My sister asked me to thank you for... ."