I really feel you on this, having a fussy eater is so stressful especially when you worry they are not getting enough nutrients. A friend of mine tried Appeton Multivitamin for her kid and she said it is easy to get the child to take it because it comes in chewable tablet form and her daughter actually likes the taste. It might also be good to mention it to your PD at the next visit, just to be safe, so they can advise if there is anything specific your child might be lacking based on their diet.