"Is it cute?"
It's not wrong, but it's more common to just write kawaii in kana, かわいい.
Many kanji haven't been entered into duolingo's accepted answers yet.
Wait until you reach the Subculture one. It's the weeb-iest course out of them all.
I like かわいいでしょうか？ Has でしょう been covered yet? It would seem more appropriate when asking for an opinion or an assessment.