Ten years. Still not old enough. To maximize nostalgia, they would have to wait until those who enjoyed the original movie have their own children of the right age, so at least 20-25 years. Which, to nobody's surprise, neatly matches the time span between original and remake for The Lion King (25 years) and The Beauty and the Beast (26 years). For The Little Mermaid, they waited even longer (34 years).