rabbitstew,
I agree, most multivits not needed if diet good, but vit d and to a lesser extent folic acid are the difficult ones to get enough of. Vitd is almost impossible to get through diet unless the food is supplemented.
WellKid baby - vit d3, best kind for absorption, also has folic acid and a range of just-for-insurance vitamins (good for fussy toddlers).
Here in Scotland, it's less than 6 months vit d making we get, and a much higher proportion of people are deficient. I am constantly telling people NOT to use sunscreen as a matter of routine but only when you are at risk of burning (even young babies!). My DC range from 18 to 1yo, and will use suncream for say, school sports day or hillwalking outings, but not for going in the garden for an hour. They had/have regular increasing exposure in spring into summer, with COMMON SENSE used rather than sunscreen. SO, dappled shade for baby, 20mins then inside at first. Sunscreens are typically full of nasty chemicals which may themselves cause cancer, so no, I'm not going to put it on my kids unless they are at real risk of being burnt.
Interestingly, people who get gradual sensible sun exposure (and lots of it), actually have lower rates of malignant melanoma than people who get no sun exposure (lack of vit d increases your risk of many cancers and a number of other serious illnesses). Actually getting sunburn is not good of course, and should be avoided.
I think, but am not sure, Holland and Barrett may sell vit D berries which are just vit d.