"~ㄹ까요/으까요" is used to suggest something in spoken Korean. Since your suggestion is not directly spoken in your question with "~ㄹ까요/으까요", it could sound politer than "~ㅂ시다/으시다". The subject is "우리/we", and is usually omitted. When the verb stem ends in a consonant, we add "~ㄹ까요/으까요?". When the verb stem ends in a vowel, we add "~ㄹ까요?"
"읽다/read" become "읽+(으)ㄹ까요?", "읽을까요?/ How about reading?", "가다/go" become "가+–ㄹ까요?", "갈까요?/Let's go./Shall we go?"