YOU SAID:
Why don't you clean your room, Mom?
INTO JAPANESE
お母さん、部屋を掃除してみませんか。
BACK INTO ENGLISH
Mom, why don't you clean the room?
INTO JAPANESE
お母さん、部屋を掃除したらどうですか。
BACK INTO ENGLISH
Mom, why don't you clean the room?
That didn't even make that much sense in English.