My sons are 18 months apart, and I was still BFing and co-sleeping when we conceived DS2, so I know what you're going through!
Our lactation consultant said there was no reason I couldn't keep nursing. She said the milk would taste a little different to the older child, but that was it. As it happens, DS1 weaned himself at 17 months, when I was 8 months pregnant. I was relieved, because nipple stimulation can bring on contractions, and also I didn't want to "tandem nurse" (a friend of mine did and LOVED it, but I just wasn't into the idea).
Anyway, we wanted DS1 to be in his own bed BEFORE the new baby came home, because we didn't want the whole family there AND we really didn't want DS1 to see a connection between new baby and exile. So we started getting him to sleep in his crib until he woke for his nightly BFing session. Then we'd bring him to bed for the rest of the night.
(Try this book: "The No Cry Sleep Solution" by Pantley -- it's got some good strategies for getting the baby (1) to sleep, and (2) to stop co-sleeping).
When I was about 6 months pregnant *I* couldn't sleep in the bed anymore (my hips got sore for both pregnancies, and so I slept in the reclining chair for the last months). I would come to bed when DS1 woke, bringing him with me. But he was really used to the crib by this point and was falling asleep there, which I think was important. We did this gradually.
His night-nurse session came later and later in the night, until it was actually early morning. And toward the end of my pregnancy, rather than bring him ME, I brought the prepared bottle. We still both went to bed. By the time DS2 was born, DS1 was used to his own bed and was weaned. And if he wanted to come into bed with us for the last hour or so of darkness, he was welcome. (And still is, lol.)
Good luck!