Thank you Tim for this discussion. You open a lot of possible avenues for further exploration. You are in an envious situation, being able to pilot different modes of delivery in your nascent program. I too like Matt's idea to incorporate weekly synchronous sessions using an external platform (ZOOM; MS Teams; Google Meet, etc.). It will give students an opportunity to connect and hear how their classmates are experiencing the program. The power of peer collaboration and assessment is too often overlooked in distributed learning programs. In face-to-face classes, much of the teaching/learning is fed by the students themselves. Students will hear perspectives from classmates that they might not have considered or perhaps have been timid to ask. The power of these invaluable learning opportunities is too often lost in course design for distributed settings. I believe that in practice, self-paced, learn anytime, anywhere makes for great catchphrases but impoverished learning environments. The self-paced model does serve certain learners very well; namely highly disciplined, task driven and motivated learners. If that description fits your learner base then this should be a highly effective model. In my experience, learners from grammar school to post-secondary need the scaffolds of timely pacing to motivate their attention and progress. What's missing in online environments is the process of meeting at a scheduled location to receive instruction with an expectation to complete related work and submit it in a timely fashion. For most of us, learn anytime means "I will do it later" which transitions to not at all.
With your program just beginning, I wonder if you are able to pilot both models. For instance, you might offer a self-paced track for students who are unable to maintain a directed schedule, and an alternate choice for those participates who prefer more peer interactive learning. Personally, I would offer the self-paced option to students anytime they find they are unable to keep pace with the scheduled class. The self-paced model would be available for those who need it.
You asked if users were allowed to message between themselves in the platform. They are, as it promotes interaction. Privacy is maintained by instructing students to to select "Hide my email address from non-privileged users" in their profile settings. Consequently, only instructors and course managers can see this information.
You are considering using Whatsapp for the instructor to announce "every couple of days a link to an activity or some other content". I find that the "Announcements" forum adequately serves this purpose. It is a one-way broadcast which e-mails students specific information from the course instructor. For other forums involving students' posts, I have given instructions on how they can edit their forum subscriptions to receive only one post per day which includes the full posts made in a day. This eliminates receiving posts every time they are made. In my courses, I also include an optional "Social forum" to discuss off-topic issues; i.e., What's going on with COVID 19 in your community?"