Hotel company here. First, my condolences for having to use Opera. What an awful product. You're going to need something like Nomadix or another gateway that is compatible with Meraki and Opera. Oracle should have a list of approved vendors, then you'll have to contact the vendor to see if they work with Meraki.
Unless you're a flag and have loyalty options, there really isn't any advantage for an independent to integrate PMS info with WiFi info. Troubleshooting maybe.