Agree with ChickenCanoe regarding starting with several rather than two.
As for kitchen scraps…..I don't have a minimum age, however I've found that chicks raised in a brooder are reluctant to try anything new without a mother hen telling them what is safe to eat and what isn't. So when I raise them they start on chick crumbles and the occasional cooked egg and that's about it until they are 3-4 weeks old and go outside to join the flock. However chicks raised under a broody hen eat whatever she suggests they eat, from day one. So if I throw out kitchen scraps, she is likely to snag a tasty morsel and encourage the chicks to eat it. All in all, broody raised chicks seem to grow up hardier and be better foragers than brooder raised chicks so I can't think it hurts them to eat kitchen scraps from the beginning.