Hi
There is a playgroup in Essen Werden, it's held on Saturday mornings 10 -12. It caters for children up to about six years old. I have not been myself for several years as with three children Saturday mornings are too busy. It was alway very sociable, most of the children came from bilingual families and were there so they could have a chance to speak English with other children.
It is called 'The Kids Club'.
http://www.the-kids-club.de/They keep their website up to date, it has the date and cotent of the next meeting and lots of info about the things that they do.
my youngest is 20 months old and I'm living in Essen-kettwig, maybe we could meet up so the children could play together sometime?
Hope this is useful!