We're also in a similar position.
Data has been tidied, unlinked contacts removed etc etc etc and now we're ready to roll SLG out!
We've had discussions about the best way of issuing usernames and passwords to parents/carers and also decided the most secure was was to do this at parent evenings. We plan to start small with parents who have shown interest in our digital newsletters and then grow the group until we release yeargroup by yeargroup.
We haven't taken any steps to prepare help documentation, AUPs, or setup training sessions for parents as of yet, but this is looming on the horizon!