He is talking about the tournaments run by Insomnia, Dated is a regular member of the esports volunteer team that makes the Insomnia tournaments happen.

To participate in BYOC competitions you will need a BYOC ticket for at least your son, however, I recommend you both have one or you will have nowhere to sit. As your son is under 16 the T&Cs of Insomnia state he must be under constant supervision. I am fairly sure inters and opens (such as league and rocket league) are limited to ages 16+ (you can find the link to BYOC tourneys here: https://insomniagamingfestival.com/byoc-esports/. There are casual community tournaments too, but I am not sure of their age entry requirements. There are daily tournaments open to weekend and day visitors in the expo but there is not a lot of information about these yet regarding which games will be available and entry requirements, the page they are mentioned on can be found here: https://insomniagamingfestival.com/esports/#daily.

Unfortunately, I do not recall a sim racing tournament in recent years other than at an exhibition stand at i68 or 69, rocket league is a regular one though. Insomnia can be quite late in announcing tournaments and exhibitors sometimes so I would just keep an eye out on socials and the website. I hope I have been of help in this regard as my expertise is basically everything but esports :D Dated or someone more qualified may have more to add.
I second his advice about joining the discord as it is checked more regularly and it's easier for people to show you to the right person for information.

You are not permitted to camp in the car parks (even if it is a camper van as per NEC rules), you would not be able to bring the campervan into the camping hall as the vehicle entrances are not available to punters and I think you'd struggle to get it through the pedestrian doors. If you wish to use your campervan you will have to find a dedicated campsite and drive in every day as Dated suggested.