"Habt ihr schon zu Abend gegessen?"

Translation: Have you already eaten dinner?

[dvdtknsn]

Is my answer wrong? "Have you already eaten this evening?"

[Menschenkind]

It's not entirely correct or wrong, although you're trying to say the same thing. Das Abendessen = dinner. zu Abend essen = to have dinner. Stick with duo's version, it's fine.