I imagine this technology would be deployed to prevent kids from visiting porn, drugs & alcohol, etc. sites. Which TBH seems fine, we already ID people at bars and adult shops.
And I don't have a problem with that. I'd have a problem if the age verification leaves a record in a database or is performed by a central entity rather than the employees of the establishment.
They would also very much like you to install their venue app on your phone so they can track your location as you approach and exit the venue.