I would use a pair of 1/2 mazzii venturis in the sump attached to 600GPH powerheads, eg a pair of cheapo Rios will work fine.

The out flow from this venturi is fed into the return pumps suction side.

That's all there is to it.
Some 1/2 tubing, the venturis, the powerheads.
The CO2 will be atomized and make no noise as it enters the return pumps.
Most will get dissolved but a little will enter as mist.

You plug the powerheads into a timer and turn the cO2 on about 30minutes prior to the lights coming on and then shut off about 30-45 min before the lights turn off.

It'll be about 2-3 bubbles a second per side/valve.
O2 should not be an issue if the plants grow well, they will add much more O2 than you possible can with any amount of aeration.

The only way to add more O2 than plants is to add pure O2 from a gas bottle.
You can do this also, welding O2 tanks and victor regulator with a needle valve etc and add about 1 bubble/sec 24/7. That should add about another 2-3 ppm of O2.

Many folks by pass the venturi and opt for a fine air stone and place that right next to the return pump suction side, this reduces the noise and produces better more even mist/dissolution.

You do not want the gas to be totally in the gas phase, you wanta nice balance between dissolved and mist.

Venturis seem to do very well there.

For the O2, it's more critical to dissolve the gas which is much harder than CO2 to dissolve(a lot harder).

The O2 gas system acts as a back up and does not displace CO2, unlike aeration.

Aeration adds a lot of noise and evaporation loss, often folks add ugly hoses and stones to their tank for this, and noisy air pump.

For a few$ more, use O2 and then have complete control. This helps the bacteria and fish, not really the plants that much.

I got a Victor O2 reg off ebay for 25$, the gas tank locally for 5 lb welding place for 35$, needle valve for 15$, (actually the reg came with a nice Nupro metering valve, so.........).

But most do not bother with O2.

Plants, good current, large weekly water changes suffice and provide awesome conditions. But I'd suggest using the O2 if you want to amplify anything there.

Regards,
Tom Barr