Last year, I was in the exact same place as you! Our second baby (Frances) came in June, and Ruby was 26 months. The baby slept in our room for about 4 months. Two months after she was born, we set up a full sized bed in Ruby's room. She had started noticing her friends having "big girl beds" and was asking us when she would get one. We didn't want to buy a toddler bed and already had this full bed. She helped set it up and helped put sheets and blankets and stuffed animals on it. She was really excited! We kept the crib in her room, too. (It was a little crowded!) I really didn't want her to feel like the new baby was taking her bed, so we took the whole thing slowly.
So, for two months she got to choose which bed she'd sleep in for naps and night time. Sometimes she'd do fine in the big bed, sometimes she wanted to go back in her crib. To make the bigness of the bed seem smaller, we would make a little nest with extra pillows and stuffed animals. She really liked that. And after a few months, she just didn't want her crib anymore. She helped us take it apart and move it into the baby's room, put sheets on it, etc. She did get a little sad about giving her crib to her new baby, but with some hugs and support, she was able to get through it. She still proudly says that she gave Frances her nice, comfy crib!
Good luck!