Check this out for an aeration system… uses a venturi to suck air into the main line, and then uses a venturi in in the nozzles to drag water into the stream and mix it with the air… I am thinking I could 3d print one of these nozzles 
From here.
The other thing to consider is an inline ‘static mixer’ like this:
with a venturi like this:
So Pump>Venturi>Mixer if you are using a standard pump or Venturi>Pump>Mixer if you are using a needle wheel pump. TBH, I think with a decent flow, just the venturi and static mixer would provide enough aeration for our needs.