Your baby chicks have a need for high protein right now. 20% for chicks is the norm. I would not start offering treats just yet to brand new chicks, unless it's scrambled/boiled eggs. There is a treat chart on BYC in the learning section that is useful.
Treats should never comprise most of the feed- unless you cannot afford to buy feed. I know that a lot of people just free ranged and fed kitchen scraps back in the olden days, but if you want a lot of eggs, this isn't really the way to go. You have to make sure they get enough protein.
Layer feed is usually around 16% protein (and also has calcium in it, so it is not for those not laying). Treats, unless they are meat scraps or eggs etc. will decrease the total protein in the feed. Treats are good in moderation- usually recommended on BYC to be no more than 10% of the feed. A handful of scratch thrown to the chickens per day is a good example.
They will really love those vegetables! The corn can be eaten whole when they are older.
If you want to give them corn now (which I don't recommend because corn is usually 7-8% protein), you will need to grind it for them. Also, offer chick grit if you are going to offer treats. Grit comes in 3 sizes at my feed store- #1 for chicks, #2 for up to I think 7 weeks and bantams, and #3 for adults. They need it to grind grains and fibers up.
Also, don't forget the oyster shell when they start laying!
Congratulations on your chicks and your fruits/vegetables!
Edited to add: I keep my new chicks on organic starter/grower crumbles until they are 6-8 weeks old, when I have found they can handle my seeds and grains.
