I would like to use Pleco's spaced repetition flashcards for myself and each of my two daughters. I can set up separate lists for each of them but would this work? Or would the system think we are one and the same person and the spaced repetition algorithm wouldnt work?
I recommend that you use three separate scorefiles, one for each person, so you can use the same cards to study separately for each person. For that, all you need to do is go into New Test, then tap on Scoring, and create two new score files named after your daughters. Going back to the main menu, you can also create three separate profiles for each person, each profile using its own score file.
You could, in theory, use only one score file and three separate categories, one for each person. But then, the flashcards in these three categories would have to be true duplicates. You would have to export the cards and re-import them into a new category with Duplicates set to Allow. But I don’t recommend that, since your separate categories can’t easily grow this way, at least if you’re not really careful to keep all flashcards separate and duplicate.
What Shun says - three separate score files will do the trick.
On a test by test basis, you can decide who is using which list; it doesn't matter. Your chosen lists might be different from your youngest, for example. The score file is the key to keeping your "accounts" separate.