Recently went with Easyjet to France and as we had a early flight (before 8.30) decided to use their late night check-in at Gatwick. Really good if you are close to the airport the night before and especially if you have kids in tow – certainly don’t want to have to get up any earlier just to queue up to check-in in bags. However, there was very little on Easyjet’s website or the internet to let me know what time the check-in closes and if all party members need to be present. Having gone to the check-in he confirmed that just one party member can be present to check in the whole part on the same booking if you have already checked in online. If you haven’t checked in online then all members need to be present. He also said that there is no close time for check-in, but best to avoid midnight as hat when the system switches over, which can cause problems apparently. That said if you have to get up early anyway your probably wanting to check-in from 8-11 anyway.
Hope this helps