Depending on where you are recording the interventions. Either the client record (young person's side) or the Family as a family intervention.
If they are on the YP side, if you mark it as secure, there is a configuration option on the ROLE details screen to stop users opening any secure interventions (that aren’t their own)
This, used with this Configuration option (in the main config), would mean that you can hide them completely.
The other option would be to use the Object sets, and for the Read Only Role, create a copy of the current object set and remove the fields you don’t want them to see.