OLCI lines at LGW

Due to take VS15 in cattle class to take the family out to see the mouse next month. What are the OLCI lines like at LGW these days? My parents went through LHR to IAD a couple of months ago and they waited just as long in line having checked in online as they would have done by just turning up.
As I'm close enough to LGW to do twilight if needed I'm trying to decide whether to use twilight to keep the kids boredom levels at the airport as low as possible. Also, if we were to try for a late (paid for) PE upgrade, would these be available through twilight or do they hold these back until the day of the flight?
Thanks.
As I'm close enough to LGW to do twilight if needed I'm trying to decide whether to use twilight to keep the kids boredom levels at the airport as low as possible. Also, if we were to try for a late (paid for) PE upgrade, would these be available through twilight or do they hold these back until the day of the flight?
Thanks.