Thanks so much for all the replies and links! I will look further into it.
Proloquo just started offering the app for free to professionals – you just have to fill in a form and upload proof of your prof registration, which I did a couple of weeks ago. It comes with ‘proloquo coach’ which is supposedly designed to guide parents through using the app, but I suspect many SLTs might find it a useful starting point too! I haven’t looked at it yet but will do soon!
If anyone is interested in participating in an informal SLT online group, where we could meet via zoom eg once a month to share experiences/adventures of using high tech AAC with young children, email me on firstname.lastname@example.org … if there is enough interest I will set one up!