Translation collaboration software for writing articles

Question

We are interested in translating articles (meaning long paragraphed text) from our language to a few of the more widely used languages in Europe.

To that end, I was looking for a way to do the following:

1. Be able to give specific people the ability to collaborate (so login and possibly permissions)
2. Manage the status (pending, worked upon, completed etc) of individual articles per language
3. Collaborate on the translation of the text where people can translate parts of the same article at the same time.
4. Easy to use (not everyone is that good with computers)
5. Preferably free

All of the free solutions I have managed to find so far are oriented torwards app/program string translation.

I was thinking to use something like Trello to do points 1 and 2 and something like Google Docs to do point 3, however that would create an enormous overhead on adding new things and managing them. I think it could get unmanageable quite fast.

I expect that for each language each pool of people would be at most 10 people.

Do you have any ideas/suggestions?