ㅂ시다 하다

"let's…," someone said

"-(으)ㅂ시다" is the polite "let's do it" proposal, and putting 하다 straight after it quotes the proposal as spoken. Every line here reports someone making a suggestion: people said "all right, let's celebrate the dads too"; "let's go up to Seoul and try something"; "let's move on"; "let's meet again in an hour"; "let's all get together and talk it over". The quoted proposal keeps its polite form while the reporting is casual.

Register: casual narration of a proposal