There is no "First time offender" rule associated with speed awareness courses. The only criteria are qualifying speed and that a previous course hasn't been completed within the last 3 years, offence to offence date. You haven't told us what the alleged speed is, but should it meet the '10% + 9mph' and the driver hasn't completed a SAC within 3 years, they should be offered one.
These things usually run smoothly, so long as the nominated driver doesn't mess about. Normally the police will not look at insurance circumstances, but a nominated driver not responding will start to arouse suspicion. At that point the police may look into why the nominated name by the insurers and nominated name by you differ.
If they do check it out, you may be asked to provide proof they were insured, yes.
Do not attempt to pervert the course of justice by nominating someone who was not driving.