As a family, you are all going through a profound process. I hope that you are able to be there for your youngest as they move into becoming who they are, and that they know it is normal for you and other family members to mourn the loss of dreams, realistic or not that revolved about them. We all have dreams to lose as we grow. There are new, and better ones to come.
And, it sure sounds as though you could use a support group yourself to talk with other parents who are going through this, other family members, friends.... Sometimes people need to deny what is going on. This doesn't usually work well over time.