The good thing about nightweaning a child so old, is that you can explain to them in words how you feel. You can straight out tell them that you and the nursies are tired and the boobs need to sleep at night. I tried this with my recent son at about 26 months, but he didn't seem ready for all night. He was very upset and cried in our arms for a few days, but he did start sleeping longer. We settled for 4-5 hours in a row and left it at that. Recently we tried again and he slept over 8 hours the first night without crying. I was shocked! I thought it would take at least 3 or 4 days or more. I congratulated him in the morning and he was so proud, then took a nice long nurse.
The second night he woke early and I told him the nursies were sleeping. He yelled at me and cried for about a minute, then snuggled with Dad because he was mad at me, and went back to sleep. That was it. After that, dad and I changed sides of the bed so he is next to DS, This way when DS wakes, he can snuggle with dad. I did hear him the other night wake up, go snuggle with dad and sing, "boobs, boobs, boobs sleeping" and then he went back to sleep. I tried hard not to laugh and wake him more. So, it is obvious he is lucid enough during the night to understand. I think it is cool to have a nursing child old enough to talk to about these things so weaning can be a much easier process than when they are younger.
Another thing. While nightweaning, I have always made sure to have a glass of water in the bedroom, in case the child asks for nursies because of thirst, and to offer hugs, so that I can be sure nighttime needs are still met. I would hate to deny the nursies not realizing they just need hydration or comfort, you KWIM. It can also help to explain to the child that the nursies are not going away forever, they will just sleep, and when the sun shines in the window, or the alarm rings (or whatever you decide), then the nursies will wake with lots of milk in them for a special morning nurse.
Good luck! I hope this helps you guys.