Atomic Anna by Rachel Barenbaum also has parental time travel as a motivation! It has long stretches of non-sci fi stuff happening too (family drama story) so may not be for someone who has more of an itch for lots of sci fi stuff. But I really enjoyed it.
Is it just one reference the Halloween costumes? Maybe the author originally had a different trio, then decided to change it, and somehow she (and copyeditors) missed getting it right? Like, that doesn’t seem super likely, but that is not an iconic trio at all…I haven’t read the book though. Could it have been the other characters icing Daisy out by making her feel foolish? Like they have come as a lion, witch, and pumpkin independently of each other and then sort of gaslight her into thinking that she can’t join them because her costume doesn’t fit?