If your Doctor retired, that is fine, the G.P who is taking over his case load will have access to the file. If your Child or children have recovered the DTC ends. However, if they did not recover then yes the G.P. will define that within the new report.
Just be sure to review the report before it is sent out. If there is anything you disagree with in the report, CLARIFY it with the Doctor. It will be fine, it is just a process that the government does to ensure people are not abusing the system if they have recovered from a disability.
Be well, and keep us posted!