Is it dangerous to give vitamins/food supplements to kids?

Sure: As long as the multivitamin is standard formula and dose for kids. However, real food is the best way to get all necessary vitamins and minerals. Fad-based food supplements are not useful to children or adults.

No: As long as it is recommended by medical experts. Children take vitamins daily as recommended by their doctors in some instances. Good luck.

Not specifically: Most are harmless and useless.They make the urine of American kids the most expensive pee in the world. Most are neither deficient nor benefitted by these products,They do not store appreciably in the body but are lost quickly in the pee. Avoid products that have ultra high amounts of vitamin A/D/E & K as they can store in the body and cause problems if stored in excessive amounts.

Not particularly: If a vitamin is formulated for children, you should be fine, but you are better off on focusing on a healthy diet and obtaining micronutrients from food instead of supplement form. Unless you child has very specific nutritional needs that are difficult to meet with a "normal" diet, I would encourage you to avoid food supplements and instead focus on the food.