Arrive in the dark or on Saturday?

At weekend rallies over Autumn and Winter do many people show up on the friday evening when it's dark? 

We're only just starting out as caravanners and we're interested in a couple of rallies near us later this year. As I have no more holiday left at work we would have to set off at about 6pm and arrive in darkness. Or arrive earlt on Saturday morning.

What's the done thing in this scenario?