When we used a side-car setup, the crib mattress was (intentionally) a few inches lower than the bed mattress, making it tougher for DS to roll into the big bed. But, it didn't do anything about waking at night...and I'd usually just have DS come in next to me to keep him more asleep after the first wakeup. We kept the sidecar until DS was about 2, then transitioned him to his own bed starting w/naps, then bedtime with one of us staying with him until he fell asleep. He was easily staying in his own bed for a while, but began coming to the big bed most nights at some point between 2 and 5am. He's 4 now, and still does come in most nights. We have a king now, which makes it pretty easy to share sleep space with a bigger kid. So, IME, starting out w/a family bed makes it pretty easy to keep a family bed...which you're not keen on. Maybe when your DS is ready to night wean, you could combine it with transitioning him to a separate sleep space?
Married to P and mama to DS (1/09)and DD (09/13 ). I'm into friends and family, gardening, exercise, yoga, reading, knitting, photos, traditional foods, breastfeeding, home birth, babywearing, and much more.