I second the opinion on Shaklee vitamins. Shaklee vitamins have been so great for my toddler. They are more complete and natural then anything else on the market that I know of and lots of science backing up their products. I am a Shaklee distributor and would be happy to recommend something for your child. My first thought would be the chewable incredivites. For kids ages 2-3 who can chew well, they can take 1 per day. Here is a link for those: http://waterways.myshaklee.com/us/en/products.php?sku=20002
Incredivites includes lactopherin, which helps with immune function. It is found in breastmilk and to my knowledge, this is the only product that has that.
If you would rather not have a chewable, Shaklee makes a very good powder vitamin for babies and toddlers. It is their multi vitamin and mineral powder. Also very complete and natural and you can add it to oatmeal, drinks, yogurt, etc.
My toddler has never had an ear infection and rarely gets sick. Shaklee vitamins and supplements has and can help with many childhood illnesses. Feel free to contact me to talk more about it if you would like.
I hope this is helpful:)