Ok, that makes much more sense, though I still seriously doubt the legitimacy of this reboot requirement. Two fairly simple options that involve slightly more downtime but should work even with your older APs:
1) If these sites can be down for ~30 minutes instead of the length of a reboot, I would simply use Port Schedules to disable the ports with access points for 30 minutes every night, which should then show up on the Device Connectivity bar if you want to double check it visually. This has the added benefit of being entirely done in the Meraki dashboard and not needing your batch script any longer.
https://documentation.meraki.com/MS/Access_Control/Port_Schedules
2) You could reduce this to ~5-10 minutes by having your script disable PoE on the switch ports, then 5 minutes later enable PoE on the switch ports, this would still bring it down long enough where it should show up on the connectivity bar.