Had to look that up...
...It's not that far away from where I live.
Give me another shout about it closer to that date. My godson likes BMX bikes so this might be fun for him. If he isn't doing anything else, I'll take him and we'll encourage your twins.
Edit: Bruce Springsteen comes to Belgium on the 13th (he plays at a festival so that's the entire afternoon + evening) so if we go to Dessel, it'll be the 14th.
Sure, I'll let you know if they decide they are definitely going there