well i do understand what your sis is saying about the kids, when i had to go through all of that, i really didn't want to live either, without my kids, it was only a short time that i had to but the wanting and waiting almost drove me insane. i remember one night i went walking and in my mind, i wanted to get snatched off the street cause i thought that unless i could stay high, i didn't want to live. the pain was too great.
i do understand how you feel and i think that you are doing a good job and that the kids do need stability, but it was the losing my kids part, that was my bottom. i got determined not to allow the state to catch me off guard with my kids being with me. the thought of losing my kids or having them become wards of the state is what did it for me and has kept me doing whatever i had to do to stay sober. now that was me, and every addict parent is not the same. i think the choice is still yours, and do agree but i also was where you say that your sis is about her kids.
as bad as it seems, if you do decide to let them go, try to make sure that the kids have a way of contacting someone if they ever need someone again.