Child activities at "De Kriekelaar"

Anyone here ever sign up their kids for activities at De Kriekelaar in Schaarbeek? If so, how much earlier than the official start time did you have to show up to make sure you could get what you wanted? I've seen that registration officially starts at 1:00 PM on Sept. 17, but I'm wondering whether that really means "better show up at 11:00 AM and stand in line for 2 hours". Thanks in advance.