my heart goes out to you as you try to deal with your wife's depression and keep your family together.
first, i think it's important that you realize you can only do so much for her. although the depression is dictating a lot of the decisions that she makes, they are her decisions and at some point you may need to detach yourself from the situation - especially for the well-being of your children, who are no doubt suffering greatly from the effects of this disease on your wife.
her doctor definitely did not do her any favors by switching her meds around without tapering. also, in my experience, some SSRI's can cause agitation. hopefully you have found a new doctor - i see a psychiatric nurse and she has a much better "bedside" manner in terms of actually listening to me and not just shoving drugs down my throat.
in addition to dealing with my own depression - which was one of the many reasons my marriage failed (my ex-husband was also depressed, so it wasn't just me!) - i also deal with my mother's depression, which she refuses to get treatment for. at the very least, your wife is trying to get help. the first thing she needs to do is find a good counselor who can help her deal with the issues surrounding being adopted. the chemical stuff - her depression - is where the meds come in and unfortunately she may have to try a few different meds and combinations of meds until she finds something that works for her. it takes time and patience.
i would suggest that you find someplace where you can have family counseling. you and your children need to be healthy too and although you're trying to help your wife, you also need to take care of yourself and your children. there may be support groups for family's of people with mental illness - that could be something to help you and your children deal with this. above all it's important that your children (and you!) understand that this is not your fault, that there's really not anything you can do to stop it, and that it's the disease that causing the problems, not your wife. of course this doesn't mean she isn't responsible for taking care of herself, but you already seem to understand that the disease is causing her to behave in ways that are "not her".
i guess my advice about getting counseling for your family is the best advice i can offer. i know from dealing with my mother that i was basically eclipsed by her depression and your children may feel that they have become invisible because of your wife's ordeal.
and now i feel that i'm just babbling.... so i'll shut up! but i wish you the best as you try to help your wife and family - but just don't think that you have to take it all on yourself! get help!!!