I am also using Pi-hole on a standalone Sheevaplug (512Mb RAM).
It’s running Debian 9 (Stretch) and is working fine (Debian is the preferred OS).
You’ll be surprised how much blocking it does and how much better some web pages work (faster load) because of unwanted ad’s.
At home, we have at least 2 smart phones, 2 tablets, 1 smart TV a laptop & PC - more when the family visit.
Wouldn’t recommend running it with Flightaware as well on the same machine, just buy a used Pi or similar for cheap and run it stand alone because as rugomol says, it needs to respond instantly.
I also set a secondary DNS server option in my main router in case the Pi-hole dies or cannot respond, so my surfing should continue unbroken.