Actually I also sleep with my baby when she's about 2-3 weeks. Is more of for convenient sake cos when she cried, i no need to walk to cot and carry her. just pat pat her by my side. Also, I also find that both of us sleep beta if we are together. I also co-sleep with my elder boy and it's true that we do sleep better too. before i gave birth to my #2, i was still co-sleeping with my son.
It really depend on what you intend to do after the CL leaves. If you intend to let baby zzz in cot, got to insist that the CL put him in the cot. let baby learn that the cot is the place to sleep.