I don't want to be a wet blanket here, but speaking from experience, running grow lights off of solar is a very tall order. My lights (LED's) pull 800w each. A day is well over 20kwh. They cost so much I stopped growing (plus, it's not legal to grow stuff where I live currently).
Also, don't run DC to your AC panel. If you just HAVE to reuse the existing wiring, I would pull each "new" DC circuit out of the breaker panel, and just reuse the wires, sans breakers (should probably add, at least, a few cheap automotive fuses). They even make pretty slick looking DC distribution panels with built in fuses, that don't cost an arm and a leg.
DIN Rail Mount 12 Position DC Power Fuse Distribution Strip Module
www.electronics-salon.com
Like someone said before, DC won't travel well over
solid wires and long distances, but I plugged in a 13v input (about battery voltage) and a 100 foot run, over 16 awg solid wire, with a 10 watt load, into a calculator. It is only a 5.6% drop and leaves you with 12.3 volts, which is plenty to run 12 volt lighting. So running small lights is definitely possible with existing home wiring, but larger loads are definitely not recommended by me.
Post some pictures of your food forest! My sister-in-law has something similar going on.