S.P.
I have 3 kids and all 3 have slept with us. With the third I was afraid the other kids would lay on her so I got the co-sleeper bassinet that attaches to the bed. They also make the original co-sleeper that is bigger. He would have his own space, but be close enough for comfort. It worked good for us.
Here is the link to the site. The original co-sleeper can be made into a playpen.
http://www.armsreach.com/