Can you say "Kommer dere i kveld?"
Why not " kommer du langs natten?
That doesn't make much sense. "bli med" means "come along." "i kveld" means "tonight." "langs natten" means "physically alongside the nighttime," which is poetic, but not very realistic.
"Kommer du med" is accepted and what came to my mind, as I always thing of "bli" as "become". Is there any difference, in terms of formal/informal or other nuance, between the two?
I thought "å bli" meant "to become"
It does. This is 'å bli med' and the preposition changes the meaning. Kind how 'to come' and 'to come to' (w/out a grammatic object; re consciousness) are completeky different.