I had my Grade 9s do a family tree a few weeks ago. They're reading a novel about someone who wants to find out who her parents are, and from where she comes.
The instructions to the students were to find as much information as they could about their relatives, and not to be embarassed by anything they unearthed. (I gave some particularly odd details about my own relatives to preface this).
Absolutely everyone in the class completed the assignment without protest. As usual, some kids did FANTASTIC work and marvellous research, while others were able only to find the dates of birth of their parents, and were feeling pretty proud of themselves when they named all their cousins by name.
One girl was initially not keen on the project, explaining that her mom had ten siblings, and all led complicated lives. I told her to find out as much as she could, and maybe do five relatives in detail. Contrary to my wildest expectations, she and her mom got so involved in the project, that she made a MASSIVE poster of all her relatives back five generations! She says that her whole famiy is suddenly very interested in genealogy, and over Spring Break, she and her mom are making a scrap book.
So, happily, no harm done, and all students did very well on the assignment, regardless of how elaborate their findings were.