I would sit them down and have a talk with them about how they are big girls now and they get to have their own bed, isn't that exciting?! Dont make it sound like you are kicking them out of yours. Make the bed as exciting as possible, with princess sheets and a canopy, or whatever works for them. Also, I would seriously consider letting them share one bed. They are used to it, they are twins, and it will make for an easier transition. Why would they want to sleep alone all of a sudden? If you have 2 rooms for them, make one the playroom and one the bedroom with a larger bed.
I just recently got my son to start sleeping in his own bed again. He is 27 mos. He used to put himself to sleep from about 15 mos- 21 mos, but then stopped when my husband's job took him out of town. For about 6 months we battled with sleep. I tried getting him his own bed, but that didn't help anything. I had to lay down with him til he fell asleep for nap and bedtime (for up to an hour!) and then every night he'd end up coming in my room. Finally I tried this:
I would do our nighttime routine of read a book, etc, turn out the light, give him some kisses, and then I told him I was going to go in the other room, but that I would set the timer on microwave for 5 minutes and I would come back to check on him and give him more kisses. I just told him he needed to stay tucked in and I'd be right back and to listen for the beep. I make sure I go back in AS SOON as it beeps and give him kisses, then I tell him the same thing over about coming back. I praise him for staying in bed and just keep reassuring him that I will be right back. I actually set the time for longer than 5 minutes if he seems fairly calm and sleepy when I go back the first time, so that after that I am usually setting it for 7 or 8 minutes. If he calls out for any reason that is real, I go back in before my 5 minutes is up- like if he needs a tissue (he has a cold). If he gets up (which he has only done a couple times, I just put him back in bed, tell him the little speech, kiss and restart the timer. He falls asleep pretty quickly on his own now instead of the half hour or more that it used to take, and he seems to sleep through the night in his own bed if he falls asleep on his own. It has worked every single time, with very little fuss. I think if you talk to the girls and explain what it going to happen, it will help. Good luck!