I can tell you my experiences. DD #1 was 2 1/2 when DD #2 was born. A few weeks before the baby was born, we changed our sleeping order to DD, DH, and me. If DD wanted to nurse, she climbed over daddy, nursed, and usually fell asleep there. Once the baby was born, we kept the order the same with the baby between me and the wall. For the first 4 months, DD #1 would go to bed first, as usual, and I would keep the baby with me until I was ready to go to sleep. She would nurse and sleep in my arms until I was ready for bed. Then, I was ready to start putting her down before I was ready to go to bed, so I would put her in a pack n play until I was ready for bed. Around 5 1/2 months, we started putting DD #1 to bed in her own bed in another room, moving her to our room when she woke up (sometime between 2 and 5 in the morning). This allowed me to safely nurse my baby to sleep in our bed without worrying about the toddler messing with her once I left the room.
When DD #2 was a newborn, I would turn my back to her to nurse DD #1, but roll back over as soon as I was done. I just felt better facing her. Around 4 1/2 - 5 months, I felt comfortable turning my back to nurse DD #1 and falling asleep that way.