2 Subnets on a network with many access points

Not with the equipment you have. You need more commercial equipment. Pretty much what you are describing is simple vlans. You have 2 virtual networks hooked to all the equipment using the cable to carry both networks.

You pretty much are going to have to scrap everything except your wiring. You need some form of managed switch which supports vlans. There are many fairly inexpensive ones. The router and the AP though are going to be a little harder. The brand commonly used by smaller installations is ubiquitii but there are a few others. Most large organizations use expensive systems from cisco, aviyia, hp etc.

I am surprised that you just use a simple guest network. Most hotel have the need to limit who can actually use the guest network because of the massive abuse by some small group of individuals.

hi, not shure but maybe this example will help you depending on equpment u you have availble

to make it simpler for presenting what i'm trying to do lets say i have modem router as frist device and wi-fi router as second device

lets say that u can configure your modem as dhcp server as network ip 192.168.2.1 (avoiding default device Ip such as 192.168.0.1) with subnet mask 255.255.0.0
configure for example internet connection (username name and password)

then configure your 2nd router with local Ip example 192.168.3.1 with subnet mask 255.255.255.0
on second device u can use dhcp as relay assigning 192.168.2.1 as dhcp server
configure your wi-fi (name and password)

now u must configure these 2 devices to work togther - hardest part. with some devices u can simply use option like bridge conection. or u must configure it as static IP. in the second scenario u can use router wan as external IP and join it in network 1 which is like 192.168.2.2 and subnet mask 255.255.0.0 and gateway 192.168.2.1.
NOTE: this is done on 2nd device
this would be result:

2 seperate networks

192.168.2.??? - we will call it public

192.168.3.??? - we will call it private

if any device connects trough wi-fi or lan with auto configuration dhcp will assign it to public network
it has internet accese and shares on that network

but for accesing our private network u must configure each device for example pc:
192.168.3.???
255.255.255.0
192.168.2.1
NOTE: some older devices (routers) can't resolve gateway even if you make it static (erlier step) and will use their local IP as gateway but your pc can go out if u enter it here

all what is left is DNS of your provider. enter it and
result is u have your 2nd network with internet accses and your shares

if u don't want to allow internet on one pc u can skip dns step or u can change gateway to 2nd device(router) ip - and i belive it shouldn't be able to go out. I know that if 2nd router can't resolve gateway using his ip would result no internet. Probably result would be the same in other case too since you are directing him to wrong address.

Keep in mind that some of this is tested but not all. Also i'm not an expert . U can see from IP adresses limitations of this example - compare it to your needs and availble equpment you have. Maybe this can be your starting piont to make something your own. Also you should think how secure it is.

I hope this helps you ...