Hi,
What you can do is configure a network alert in the Meraki Dashboard which sends out an alert email when one of the specific clients connects/disconnects from the Lan (this also works for VPN Lan clients). The VPN clients need to be connected at least once before you can select them of course.
Go to Network wide -> Alerts -> WAN appliance. Select the VPN client hostname or MAC address, and fill in the desired email address in the recipients:
This will keep you updated on all client VPN user/device activity through emails. For a real report you will need to add external tooling/application to poll the Dashboard through API or to receive certain alerts, and create some kind of report based on these. Another way would be to collect the syslog on a seperate server and create the report there with tooling/scripting.
Cheers