There are alternatives to Depakote that may have less lethargy and drowsiness. Ask your doctor about Topiramate or Gabapentin or Lamotrigine. All of these medications have side effects and cause some drowsiness, but they vary from person to person so trying another may be the solution you are looking for.
You and your son have a particularly difficult problem to manage. Ask your doctor to keep trying to find the right mix of medications to balance everything off. It will take time, constant management and periodic change of medications so stay vigilant and keep close contact with the prescribing doctor.