Hi @safefirst
Yes, definitely speak to LADO before governors. Govs will seek advice from LADO and their response will ultimately be to relay to you what LADO has told them. You would be far better hearing it directly from LADO, asking questions etc.
Safeguarding investigations can be concluded as:
Substantiated (it happened, it was wrong, HR have taken action but school not allowed to tell you what)
Unsubstantiated (ie did their best to find out what happened but came down to one person's word against another)
Unfounded (eg the actions which left the finger marks were reasonable - ie restraining him from hurting himself even more badly)
Malicious - you or he made it up
False - probably false - it never happened, (eg proof that another child did it).
To start with, you need to properly understand what conclusion the school/LADO came to, so that you know what to complain about.
If substantiated - they certainly should have taken action (written warning?), but can't tell you exactly what due to HR confidentiality. You could complain that the actions are not sufficient, particularly her being around your son. This would be the strongest complaint.
If unsubstantiated - they are a bit stuck. They may 100% believe you and be worried about the member of staff, but can't prove it. Cue a protracted negotiation with the staff member/union about actions they tried to take but which could have been seen as unfair treatment by the staff member. These are the hardest for heads to deal with. The only reasonable complaint might be that they could have investigated better (witnesses not interviewed?); HR will have ultimately advised what to do with the staff member and (legal) options will have been limited.
If unfounded/malicious/false - then why?
A complaint to governors will almost certainly come back with whatever LADO has to say about the case, and there is usually no mechanism to appeal if you want to go back to govs with a response to their response. Better to understand what LADO has to say and - if you remain dissatisfied - to address those points in your complaint.