We are using vitamin D drops for the first time with our nursing baby & these were the ones I heard the best things about, Carlson Labs Super Daily D3 for BabyI am really impressed. I was skeptical at first about needing the drops for a breastfed baby but after I read up more about the benefits of Vitamin D and talked it over with my midwife I felt good about it. I asked some wise mommas around here and these were the ones most often suggested as they are tasteless, need one drop (vs. a dropperful) and don't have all the nasty tasting additives of the other brands. There's also a higher concentration for your big kids, Carlson D Drops and those are 2000 vs. 400 for the infant. My big kids, oddly enough, beg for the baby's drops because they think it's funny for me to drop it on their tongues so I need the older drops for them. My midwife advises 5,000 for pregnant and nursing moms so we just do the capsules we found in bulk at Sams.
Do your research, see what you find, but these bottles with one drop doses last a year (I'll see if that's true with my kids trying to help themselves!) which makes the price the best I found.