Your design issues and solutions are correct. You need a switch/router that can handle multiple VLANs,
and use different Client VLANs per WLAN, than your APs and ZD management network. Your APs then
go into switch Trunk ports, servicing the number of Client VLANs and your ZD/AP management VLAN.
The Captive Portal for guest/customers, allows you to pop up a Greeting (terms and conditions), and
drop them on your desired Advertising page (perhaps) or their intended homepage, for their browser.
A Hotel might require a guest pass authentication, but a Store typically would not.
More info about assigning VLANs (page 241) or Guest Access (captive portal, page 368) in the latest
ZD 9.13 (GA) User Guide:
https://support.ruckuswireless.com/documents/1106-zonedirector-9-13-ga-user-guide