Well, nobody showed up but my girlfriend and I... But that was okay, we cleaned up the entire park in an hour and a half. We must have taken ten kilos of broken glass and metal shards out of there, not to mention all the other random junk and bottles. It feels good to know that it is a safer place for kids to play and that it looks much better. I will try to arange another cleanup day and maybe we will get some people to come help.
PS. Not that we shouldn´t continue to watch out for them, but we didn´t find a single used needle. Just broken glass and metal.