Here's an idea that might work around the problem (for us): create a virtual "proxy" device for each of the child devices, then use that virtual/proxy device in any app/automation/dashboard/etc. where you want the "real" device. Then, use an app or a rule to "sync" the two. I think the Hampton Bay Fan Controller driver is still the "old school" dimmer-style driver, so something like the [RELEASE] Switch Bindings app might work; otherwise, I think Rule Machine (and/or maybe WATO?) can do something similar, as could a simple custom app if desired instead. Pretty sure this would work for the lights (just a dimmer or on/off if that's all you have set) as-is.
If the Fan Controller ever changes its DNI and messes up the child devices again, you can just go into the Switch Bindings app (or your rule, other custom app, or however you have this set up) and switch out the real "bound" device with the new/correct one. Since you'd be using the "proxy"/virtual device in all your automations, you'd only have to worry about it in this one place.
Hopefully we can get something better for child devices in the future, but if you want a workaround for now this seems like something that should work. 
I'm doing something similar but for totally different reasons: I have a few smart plugs that get different uses depending on time of year (and my whims), so I'm using the Switch Bindings app above to tie a virtual "proxy" device to a "real" smart plug, avoiding the need for me to re-name the smart plug device and re-work my automations every time I change my mind about something.
