Can I give prenatal vitamins to my children?

Better if you don't. Prenatal vitamins contain a lot of the same things, but in different quantities that are more appropriate to a mom than to a kid. They are also in forms that children will generally find less palatable than vitamins designed for children.
Not a good idea. Prenatal vitamins are formulated for the needs of a pregnant woman's body. Children's bodies have different needs. Your prenatal vitamins contain substances and dosages that are not correct for your children. Dispose of them and get you children vitamins that contain the correct dosages for children.