Hi, Dominique.
There is a way to use a link that makes a copy of a Google Doc you have created. It requires some manipulation of the URL. Here is a guide. I'm not sure if this works for other GAFE apps. You could then share the link using the URL resource in Moodle or from within a Page resource that includes other instructions. This method would be good to provide a template of an activity sheet, but it doesn't share the document copy with the creator, so you can't track what the students do in their copy of the Google Doc. If you wanted students to submit this for assessment, you could get them to submit the document URL as an assignment submission. The other downside of this method is that if a student hits the link more than once, they will end up with a new copy each time.
If you want your students to collaborate on a single Google Doc, you can create the Google Doc, sharing it with users in your institution, then use the URL resource, with the Embed setting turned on. If you wanted to limit it to a group, you could use Moodle groups to control access to that resource.
I find limitations in each of these methods. It would be good if there was a more natural support for this in Moodle, but I can't blame anyone for that but myself.