(((((hugs))))) If the decision were up to me, I would tape Duckie performing and have that playing. But you do need to discuss this with Duckie and see what her feelings are. though the final choice should not be hers at this age, in my opinion.
PLEASE get a digital voice recorder or old fashioned tape recorder and get mother in law talkng about her childhood, when yoru husband and his sibs were kids, any/all family memories you possibly can get her to tell. If duckie is up to it, maybe let her take a morning or afternoon off of school to record her grandmother's stories. Those tapes will mean so very much in the years to come - to you, husband, his sibs, Duckie, and even Duckie's children. I know because we have some of my grandparents on mom's side and my great gma on dad's. At one point we sent cassette tapes to my grandparents instead of letters, and they sent some back. After my gpa was dead for a year or so, my gma gave them to me, along with her recipes (she hated cooking but had a stash of awesome recipes). At a couple of different times I copied those tapes and some of stories that they told to me on vacations and sent the copies to my cousins and aunts. then I did the same with the recipes, only they got xeroxed so we all have the handwriting, not just the recipes. They are truly family treasures to us, more than her jewelry or dishes or silver.
Please save these memories now. It will mean so much in years to come. Duckie will enjoy sharing them with her children too. My kids LOVE listening to my grands tell the family stories.