One of my 3-year-old's favorites is mini-quiche (aka egg pie.) I
simply beat eggs with a little milk and salt and pepper. Then add
finely grated veges like carrot, broccoli stem, zucchini, etc. and a
small amount of grated cheese (you could certainly leave that out.) I
bake them in a cupcake pan, or my new favorite silicone pan with swirly
shapes. I freeze the rest of the batch in a Ziploc.
My son likes them best at room temp, so now we just let it thaw in his lunchbox.
Other
favorites are turkey breast lunchmeat rolled into "sticks." Also
carrots, celery and cherry tomatoes with a little ranch dip. We also do
mixed nuts for protein as a "side."
I"m also a huge Veganlunchbox fan! And non-vegan too.