I'm not giving vitamins either, I didn't with my older kids and don't plan to start now.
For one thing, D3 is supposed to be taken rather than D2 but D3 is animal derived and I'm vegge/vegan. For another, I firmly believe in & honour the virgin gut, and you can't get vitamins that are just the vitamin, they all contain other stuff and I'm iffy about that, my baby is getting nothing but BM til over 6 months old.
I'm also not convinced how much of oral supplemented vitamin D is bioavailable. Chances are it's not a lot.