We do. Last winter I took 2000iu/day myself, and figured baby would get some through BF. This summer I stopped taking it, but did not get enough outside time, apparently, because we tested quite deficient this fall. We spent some time outside every day, but I tried to avoid going out at midday to avoid sunburns. And she naps in the early afternoon. So she really didn't get a lot of strong sun. So now I take 5000iu/day myself and give my 17mo 1000iu/day. We'll check our levels again in a few months and see if it helps. We may lower the dosage once we're less deficient.
In most of the northern half of north america, there is not sufficient sunlight to cause vit D production in the winter months. Your body can store vitamin D from summer, but most people don't get close to enough exposure (without sunscreen, to direct sunlight) to do that. Keep in mind our ancestors (who lived without supplements, lol) spent nearly all day, every day, outside, mostly naked, without sunscreen during the summer. And darker skinned people (who need more sun to make vitD) lived farther south where the sun is stronger.
The drops are super easy too. They are tasteless (I tried one) and I can put a little drop on my nipple before nursing.