I have now relactated twice in preparation for adoptive breastfeeding. The first time my output was minimal, but likely would have built up to something more substantial over time. The second time, it was like I had given birth, and I'm really not sure why, and I know that's not the usual outcome. I had to quit, I was so engorged, and the little girl we were adopting died of malaria (or her dad changed his mind, or the whole thing was a scam, we'll never know) and we were many months away from having a baby home. Once we were matched with kids I realized that I would have to maintain a pumping regiment in africa, while trying to bond with our two new kiddos, who would both be at the age where it would be iffy at best whether they would even nurse at all... so I gave it up.
I guess my point is, I was really dedicated to adoptive nursing, but the logistics just made it impossible. If you would rather nurse your child than adopt an HIV+ child, keep in mind that the logistics with Ugandan adoption are such that it might be difficult to nurse anyway, so I wouldn't bank too heavily on nursing. I'm not trying to be discouraging, but if you compare the health benefits of breastfeeding with the health benefits for an HIV+ child being adopted into your family... there is really no comparison, ya know?
I know you're still in the consideration phase, just wanted to share my own experience!