Now that looks like a lot of work!
They can't walk around and eat/drink by themselves like chicks and ducklings, right?
How much time daily would you say they need?
A lot of work! They really are still just a little foetus. Initially hourly feeds and I'd leave them 5 hours overnight. Only half their crops are open to start with but that slowly opens up so they can eat a little more. As they grow the time between feeds gets longer but even as older chicks almost starting to wean they still need 3 hourly feeds. The Javas are a bigger finch anyway so much easier to keep alive than the tiny ones. But they are very sweet so it was well worth the effort.