M.H.
I was in the same boat as you. My daughter was 17 months old when my son was born (I was 22 at the time) and we moved her into a twin sized bed about a month before he was born. She did fine!! I laid in bed with her the first few nights just for 10 mins or so and that was it. A little later we started putting a baby gate up on her door cause she was sleep walking, but thats another story altogether. Now Im expecting #3 in January but we moved my son into a big boy bed when he was 18 months old and it was the same situation. I laid with him for a few minutes every night and then just let him do his thing. Both my kids sleep in regular beds (we didnt see the point in toddler beds) and its was a piece of cake. Have fun!