A seemingly simple Japanese conversation

The word "いい" in Japanese is very difficult to understand. Sometimes Japanese people have to repeatedly confirm whether the other party is "ok" or "no need".

The "おfather さん" here means "いいねえ" and the "ねえ" indicates a tone of approval, so it is the father who wants to drink tea. My mother's "private" means "I won't use it."

For reference!