You don’t want to use pfSense for WiFi. I mean you can… but its not really made for it well. You can easily plug Ubiquiti equipment into a pfSense firewall/router.
There’s lots of things to think about.
What is their budget?
You should identify where there connectivity issues are from. That will determine where they need to invest in upgraded infrastructure. If its ISP related, nothing fill fix that except the ISP.
you have to keep in mind that while solutions like pfSense may be cheap(ish), you’ll have to maintain it through its lifetime, is this an option for you? More standard equipment will be easier for others to also maintain (other professionals, not the medical staff). Whos manages there IT equipment currently? Or is this a makeshift network of 10 people where the ‘IT guy’ is the guy who first bought a laptop?
If it is primarily a wifi issue causing the connectivity issues then Ubiquiti isn’t a bad solution, they are easy to manage, and work quite nicely. Yes not fully open source, but your not getting this unfortunately. there are some alternatives though (forget their names)
While you can go all Ubiquiti, there may be better and cheaper options on the switching and routing/firewall side. There wifi stuff will run fine on any infrastructure.
Need to consider how many users are there, usage, ISP bandwidth available to take care of them all. How many wifi devices, how large an area do you need to cover, etc.