Help with CPE mode

I have a wAP ac on my boat which I use to connect to the marina WiFi when in dock, or LTE when sailing.
This is wired to another hAP Lite that acts as a network switch for my devices and access point for guests etc on board.

To get this to work I scanned the 5 GHz range to locate the marina’s APs, and there are several in range on different frequencies, as well as a host of other devices (some hidden - CCTV system) as well as other boats, I selected the one with the best s/n ratio.. There are also some 2.4 APs used by the marina.

The SSID and Password is the same, so I have set this up in the Security Profile.

What I would like to be able to do is allow the client to select the best signal, across both bands if possible, or at least prioritise the 5 GHz ones, but fall back to the 2,5 GHz if necessary.

To make matters worse the Marina is making changes to the network as it grows, and I am accessing my systems remotely, across the WiFi connection, so I are worried about loosing it if they reassign frequencies etc.

If someone could point me to the best (and safe) way to ensure I have connectivity.