Hello, first off, congrats on the breeding fish
I've raised baby goldfish many times, and I'm just a hobbyist...
from my experience, its best to combine many types of food, both animal and plant based.
here's my setup:
a decent sized aquarium with air driven sponge filter, make sure the current is not too strong for the babies
I put in some floating plants like hornworts or anacharis, for their dense bushy-ness stores a lot of micro food that the babies can pick off in their leisure and provides shelter as well (not to forget providing extra oxygen and filter)
for feeding I let algae grow on rocks and side of glass, I also fed them boiled egg yolk, mushed up and scattered evenly. my tip, is to boil a couple of eggs, store in fridge, and only use when necessary.
you know, there are also liquid emulsion food specially made for young fry, sometimes I use liquifry for my tropical fish babies, but my goldfish was never raised with them and they're just fine
good luck