L.D.
My first thought was the gummy vitamin idea too. Costco stocks great multivitamins and also calcium vitamins (both L'il Critters brand) . These are what I give my kids. Secondly, I know your pediatrician can prescribe liquid vitamins that you can put in his drinks or applesauce. This would be easiest way to go. You can also research over the counter liquid vitamins and find what you want on the internet if you look hard enough .Start with the drug manufacturers and move on to vitamin websites. You should be able to get vitamins into your kid without too much trouble. Good luck!