I do understand what you mean; sometimes it is difficult to decide what to do for the best. I recently found a young magpie who appeared injured but I wasn't sure.
I went back & forth several times to check on him before deciding to take him home. Luckily I made the correct decision as he had a damaged wing. The receptionist at my local vets took him in after the vet treated him. When i spoke to her the other day she told me that he wa smaking good progress & had been moved to a large aviary. Hopefully he'll be released in a month or so. Good luck with your chicks!

*Update*

Sadly one of the chicks passed away(the male) a couple of days after i posted this. His sister is alive and kicking though! we are onto one feed every 3 hours now give or take. she churps for me to come and feed her. I have been trying not to handle her very much although she is usually hesitant to perch on my hand whilst i feed her. she is put into a larger run in the day to practice flying and churps to the other birds. In a week or so i should have a large night time chicken run i am going to put small mesh on it and in the day time she will be in there. i will keep her in there until she is feeding herself and then i will eventually open it up but leave it available for her to come back for food etc. I have been reading lots on re-releasing and as there where no places near to me and knowing that some of her relatives and neighbours are still nesting in the same tree it would make much more logic sense to me to release her back with her own gang in the hope that they may take her back once she is feeding herself. Oh and she is not a greenfinch!! she is a siskin!