Hi chirstoph. You may have found a package already, but if not, let me point you towards http://www.ploughas.com
The website used there is a full package, with a big future set out with loads more features. The package allows the user/membership records to be integrated into the website, leading the way for excellent content.
Please browse around and also look around the "Reports" area to get an idea of how powerful the software is, even in this humble stage.
There is an Administrator area which you would restrict to your authorised members (committee members), where the site (and member records) is maintained.
If you like it, please let me know and we should be able to see what we can do.