Unifi Guest network in multiple locations


I’ve been asked by a customer to spec a Guest Wifi network for 4 coffee shops she owns for customers to use.

There is decent broadband at each location and existing devices like tills and office pc’s are all hardwired at each location. Currently no wifi at any shop.

My questions are

Is it possible to install an Unifi AC Pro in each of the locations and enable just the Guest network option for customers to use.

Do I need to have a hotspot or portal option? She does not want to charge for the wifi.

Where do i locate the Unifi controller? Does it have to be a hosted controller on Digital Ocean? or would a simple Cloud key located at the Owners main office suffice?

If the cloud key is an option is it just a case of setting all the access points up at the office then installing on each site? Do they automatically connect back to the controller? or is there firewall ports that have to be opened at each site

Apologies for so may questions at one time. Any advice would be great.

For guest network captive portal is not needed and the simplest way to manage them would be from a Hosifi account https://hostifi.net/?via=lawrencesystems as it does no require you have any knowledge of how to setup or maintain the controller, they will take care of it. Because each of the access points once adpopted are reaching out to the controller there are no special firewall rules to configure.