I got a baby cake and it solved the "what treat to give" thing for me. I want to wait till they are older before giving vegetables etc. and their bodies get strong to handle all the different foods.
http://www.wildbirdsuets.com/foragecakes/babycake.htm
It says to give it to them little by little 20 minutes at a time the first few days.
Day one they were terrified of it. Day 2 Funky May got brave and pecked at it and then started a feeding frenzy lol, now they wait for it and have a blast pecking at it ( 4-1/2 weeks old)