Our situation is that we're having twins, AND DS is not ready to sleep on his own all night and we are not ready to ask him to, so he will be joining us at some point during the night. We have a king so space is not an issue so much as safety. If I was having a singleton I'd feel very comfortable co-sleeping in our family bed with the baby on my arm, but with two newborns, I'm not.
We were planning to sidecar a crib but after reading more about how to do it, I am not convinced we can do it in a way that's safe for newborns. (Please, if anyone has figured this out, share!) I think it would work wonderfully for 6mo+ and we may do it at that point. But, I just don't see a way to close the gap between the crib mattress and the big mattress safely, at least for our bed setup. There will always be some kind of gap, and/or a gap between the spacer (foam or rolled up blanket or what have you) at the far side of the crib. It's just what they say to look out for in older cribs - bumpers and slits. Personally I would love to just put all the mattresses on the floor but DH is not into it. So our tentative solution is to put our pack n play right up next to our bed, essentially like a co-sleeper. (I went to see some at the store and I don't really get co-sleepers...they are just a pack n play with one side that is a little lower, no?) We already have one so might as well try it. If the babies are anything like their big brother, they will accept nothing other than sleeping on me, but we'll see if they enjoy sleeping near one another. If not I plan to sleep with one on my right arm, DS in the middle, DH on the other side, and put the other twin in whatever safe sleeping space he accepts (probably an inclined one like the rock n play thingy, if experience holds.) Then I'll switch them out when they wake to nurse. I've also heard from other twin moms that you can put both on your arm. I felt very safe doing this with DS, he never moved and I always sensed him very well. My mom slept with us this way also so it helped to have her experience.
FWIW, we didn't start out committed to co-sleeping, we were just committed to whatever worked, was safe and got everyone the most sleep. At first I worried I wouldn't sleep well with him but my personal experience was that I could not sleep without sensing my baby. If he wasn't next to me I was just panicked about where he was and if he was breathing. I grew up with co-sleeping so I was very open to it, and when the baby wouldn't sleep any other way it was fine with me. DH very much did NOT grow up with that being okay, but he was open-minded about it and has come to really like it as well. Our almost-5yo obviously still sleeps with us and honestly, I get sad thinking about when he doesn't (though obviously I want him to, when it is time). I think if this is an uncomfortable thought for anyone, that is completely fine. Your feelings about it are really important. If having the baby sleep in its own space is really not working, you can always try it and decide at some point that is comfortable to you to "wean," just like some people BF for 12mo and others for longer. As others have said, intimacy has never been a problem. First, DS starts the night in his own room so we don't even do anything that unusual. And if it's getting late and we want more assured privacy, there is the living room downstairs. But I think if this is something that you might feel resentful about, that is legitimate and worth addressing.
JENinOR, I really like the guidelines you linekd to. Most guidlelines say not to have ANY bedding at all (no pillows or blankets for the adults).