I don’t have anything to add, other than to say this also confused me. Even though I know 言っとく = 言っておく, I still don’t understand how it fits into the sentence.
Googling 「一応言っておくと」brought up some sites saying things like “just so you know/just letting you know”, which seems to fit with her explaining the reasoning about red lights affecting the time it takes to travel the 50km
Interesting, because to be honest, I wasn’t sure what the 一応 was adding either searching for the contracted 言っとく gave me 言っとくけど, meaning ‘for your information’, which also seems similar.
Alright, I got this…
一応 = “just in case”
言っておく = “to say in advance”
と = generic conjunction
一応言っておくと = “Just in case, I’ll say it in advance…” = “just so you know"
Depends on context. Obviously 俺ら isn’t polite, but 彼ら is fine. It’s also fine in technical Japanese: @Belthazar ら Belthazar et al.
I totally forgot to post this before. It’s a trailer for the new Non Non Biyori movie, but the end has a nice callback to this chapter.