I totally know what you are going through. I'm not even pregnant yet, and am looking forward to nursing, but there's no way I can nurse both of them at night. . .even mommy needs at least 1-2 hours a sleep to function!
My dd is cutting her eye teeth right now, and is up A LOT at night, and although it's frustrating, I know it's only temporary. . .and that helps me get through it. I've thought about night weaning, but a few nights ago, I told her that yum yums went night night, and tried to rub her back and comfort her and she got hysterical, screaming YUM YUM PLEEEEAAASE!!! who can refuse that?? I know she's not ready to night wean for sure, and I would need dh's help which he can't do right now. . .so business as usual for us at least for another few months.
As far as potty training. . .I dealt with this with ds and being pregnant with dd, I knew that I wouldn't be able to "drop" everything and help him go potty 5 million times a day, so I put it off, would let him "try" in the mornings when I was getting ready, etc. But never asked throughout the day. . .once baby came, then daddy left (military) daddy came back, and we moved to new house. .. about 3 weeks into our new house I put him in training pants and he had a total of 3 day time accidents, and after about 1 month of him being dry overnight I put him in trainpants at night too, and he's only had 3 night time accidents too. We were all ready a the same time. He was 2.5 at the time. Good luck!