Mixing vitamin syrup to milk

I don't think it will matter. Just be sure that she isn't overdosing the boys. Overdoses of vitamins can be even more harmful than deficiencies! Most people nowadays tend to overdose and have all kinds of symptoms and damage from it. If they eat a good diet with plenty of colorful vegetables, greens and proteins with whole grains, they probably don't need many supplements. One huge deficiency most people have is Vitamin D--mainly because most of them avoid the sunshine and when they do get out they slather on the sun block. The D that is added to milk and cereal is D2, which is inferior to the natural D3. Do some research and look up the amounts the boys need if it really bothers you then figure out if they're getting what they need. Any more than the recommended could seriously compromise their health!

It doesn't matter how you take your vitamins. I take mine with a meal. It's easier on the stomach. I have a sensitive tummy. If the kids don't mind the taste of vitamin milk, it's not a problem. Just be sure they are getting the right dose for their age.