Kids sharing room (baby and toddler)

So I’m having a dilemma. I have a 3 year old and 12 week. Currently our baby sleeps in our bed 95% of the night cause he just won’t stay asleep for long stretches. We only have my daughters room and our room. My doc said to have them share a room cause around this time baby understands where he’s falling asleep and to do it where you want him to be sleeping a year from now. I don’t want to disturb baby when I get up to pee or when my alarm goes off for work. I’m just nervous about moving him into her room cause how do I get them both to sleep at night and without baby disturbing my daughter cause whenever I try to train him to sleep it will requiring some crying. She gets really bothered when he cries in the car. She’s also not very quiet getting ready for bed. Also when baby cries in the middle of the night I’ll have to go in and feed. He’s waking like 4 times max depending on the night. It’s going to disrupt her sleep until she gets used to it. I’m just so stressed. I wish he was a better sleeper and can be okay being placed on his back alone in a crib. So I’m just asking how did it work for those littles sharing a room, bedtime routine and the during the night.