How can I reserve a WiFi hotspot?

Question

WiFi

There is a hotspot in the cafe. A piece of iron (presumably ASUS + LTE whistle) distributes WiFi to visitors. The following problems are possible with it (in theory, I list everything) - freezing of the router, freezing of the whistle, power failure, breakdown - like everything?
The question is how to protect yourself from these problems? Remote if possible. The staff of the cafe does not understand technology. The power supply is backed up by the UPS. Or there are routers with a battery? Breakage - replacement. What about hangups?
You can put a second router in another corner of the cafe. But how then to dock them together in case one freezes, so that the second one supports users from the first one automatically? SSID to do with one name? Turn on the second, like a repeater? What are the general solutions on this topic?
Do not offer CISCO routers with mutual redundancy - there the budget is far beyond.

Answer 1

Did at one time a similar task, only at the gas station. I used Mikrotik + Huawei E3276.
+ router freezes - WatchDog is present
+ modem freezes - script pulls usb power when there is no ping outside
+ breakage - mikrotiks are quite reliable
yet:
+ Captive portal: the client had to watch ads before getting the Internet
+ queues: one client will not take up the entire Internet
+ in an openvpn server was raised on the Internet, where all mikrotiks were connected if there was an Internet, it was possible to control them remotely (the operator gave out gray IPs)
against "bad" sites used Yandex "children's" dns
cons:
- you need to be able to cook mikrotiks
- compatibility with a particular brand of modems should be checked individually
The second access point will not help without a second modem, who will give it the Internet if the first one collapsed?

Answer 2

If the budget does not allow, then there is practically one way out:
-Try turning it off and on again. Does not work? Try turning it off and on again

Answer 3

Konstantin, the budget does not allow a cisco for 100+ thousand rubles. 2 normal routers fit perfectly. Now give a normal answer?