Maybe you should get a second opinion. It sounds like your doctor doesn't have a problem prescribing all this medicine to kids. They are still growing and not a lot of this stuff has been tested long-term.
I don't know your kids, so I have to ask: do they really need all this stuff? Is there behavior really so bad that they need to be so heavily medicated?
Are they seeing a child psychologist who may be able to do behavioral therapy, rather than so much medication? Maybe there is a reason why your daughter is so aggressive. Is there any thing in her life that would cause her to act out in that way? Death in the family? Divorce? Feeling like she doesn't have any say in her own life? Anything? Take her to talk to someone and she may open up and feel better. Same with your son.
Plus, by telling them they have a disorder, they may not feel responsible for what they does. How does that teach self-control? Just a thought.
Good luck with everything. I know it's difficult to figure out what to do in this situation. So many parents are in your shoes.