Is sun bathing still recommended option to get natural vitamin D for infants or one should prefer the medications like Vit D3, calcitrol etc. Also which sunlight morning time or afternoon time is most beneficial?
While getting Vitamin D is important, remember that how you get it is important, too. Sunlight has other characteristics.
But, I am not a Dr, so let me share a pretty comprehensive site that covers this in detail: http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
After reading that, you will most likely know more than you ever wanted. :)
Importantly, the sun section concludes with this:
Assessment of vitamin D requirements cannot address the level of sun exposure because of these public health concerns about skin cancer, and there are no studies to determine whether UVB-induced synthesis of vitamin D can occur without increased risk of skin cancer.