Not sure if this helps as I don't have twins....
I have been dieting hardcore now for about 1 1/2 months. I had my 2nd daughter in Nov, but couldn't exercise for a few months afterwards due to a prolapse. (Fun times!) Once I could finally start exercising, I cut my calories to 2000. I was so afraid of my supply being too low. But eventually I started cutting back more, and now I try to average about 1600 calories a day, while also exercising (usually running about 20-30 minutes a day). I have been steadily losing about 4 pounds each week since I started. I haven't had any problems with my milksupply, and my little one eats ALL THE TIME.
I would also suggest Mother's Milk tea -- seriously one cup of that stuff and I am leaking out nonstop. I bought in just in case my supply decreased, and it is amazing. Literally one cup, and then I am a fountain. I know there are also fenugreek supplements you can buy (same herb that is in the tea), that is supposed to do the same thing.
Congrats on your twins!!!