I am sure you have gotten all kinds of advice by now, but I will give you my opinion of what I would do.
I dont want to sound harsh or anything, but sometimes tough love is the way to go. And yes, for the record, I was a breastfeeding/co-sleeping mom.
Just remember that whatever you do at this point is going to be a little more difficult than if you had tried this a long time ago, before you got pregnant.
AT this point, he knows something is up and senses the change and will fight it to the end. He might be a bit more clingy and jealous, something is telling him that your body is no longer for him, but for the new babies.
The best option would have been to start weaning him while ttc'ing and also training him to sleep in his own room. That way, once you were pregnant, he would be in that adjustment phase and by the time the babies are born he would be safe and secure in his own room/bed and drinking from a cup. That would be in a perfect world :)
But seeing as time is of the essence at this point, the whole process just needs speeded up. Make sure he gets plenty of fluid thru the day so maybe he wont wake as often at night to bf. But keep in mind, the night time bf's may be mostly about the connection than the nutrition. You can try both things at once, weaning and non-co-sleeping, that might work. I wouldnt suggest he goes from your bed to your floor either, as down the road thats one more transition for the both of you. Put him down in his room and offer a drink when he wakes and try patting him, or sitting by his bed til he falls asleep. Each time he wakes, sip, pat, sit. NO talking after the first couple of nights. He is old enough to get the pattern. YES, it will be torture and it might take a couple of weeks. But if you stick to anything long enough it will work. I just hope that you can accomplish what you want before the new babies are born.
Best of luck. I hope whatever you decide to do works.