Hi Samantha
This requirement is a hassle even for those of us who live here in Spain, as evidenced by the reports that only about 12% of owners of even registered properties are actually complying at the moment! I spent several months unsuccessfully trying to get an appointment at the Comissaria de Policia to get t1he password you need to log in for online guest registration.- I'll try again in a few months when I've summoned up the will to live again!
Do you have someone who meets your guests when they arrive? If not, it will be more difficult to comply with this. You could send them a form to fill in online in advance, but people are, not surprisingly, often unwilling to do this.
However, there is a company here that has a system of checking-in using a mobile phone and they seem to have added a system for absent hosts using a Q-code. Have a look at their website: https://www.checkinscan.com/en/
and see if that would work for you. I think you would still have to go, or get your lawyer to do so, to the police station to register initially.