They're great. I use them myself. They offer full guest access option with a splash page and captive portal that logs your sessions.
The firmware is loaded onto the UniFi AP and gives you guest access options and an unlimited number of SSIDs (guest and private networks).
Their dashboard lets you create a splash page and charge users via Stripe or Paypal (cash is also and option).
You can try them for free. I hope you like it.