Ah I am so happy to see that your community is making the decision to move to Discourse. If I can provide a few loose suggestions based on your well-written post above…
Category decision fatigue
I personally think you could have a few too many categories. One problem with having that is there is room for confusion for a new member, and posting becomes slightly difficult, like a barrier of entry even before writing because they feel they have to choose the correct category.
What I would suggest is a few basic categories
- Welcome
- Care
- Grief
- Off-topic
… then a heavy use of tags. Tags are simpler, as they can be added after a topic is created by moderators or other privileged users.
When the number of posts start to grow, they naturally start to show better ideas around organisation, then you can create new sub-categories, use bulk-select and move them all into a new category if needed.
Attachments
Don’t forget attachments! There is an authorized extensions site setting that you may want to modify based on what your users share, e.g. pdfs for bloods / reports.
Migration
Does Facebook provide you a list of emails / join dates? New member signups tend to be severely limited in posting, so you may want to include some form of base TL (trust level) for people who have been posting in the old community and are ‘veterans’.
You can check settings in
/admin/site_settings/category/postingand/admin/site_settings/category/trust
to see if they are too limiting.