We sleep on one of his blankets. It's big enough not to bunch with both of our weights on it.
Your post leads me to another question. Do any of your doctors frown upon cosleeping? We just had our 2 week appt and he gave us/me a guilt trip and "horror stories". I tried to get him to do the crib last night. After a few hours he just ended up in the bed again. The lack of sleep and failure to have succcess with getting him to the crib at all have not been helping my baby blues I've been experiencing. My hubby is concerned since I've actually had severe PPD with my 2nd pregnancy.
It's really none of the doctor's business. If I wanted parenting advice, I'd ask for it. My pediatrician's job is to handle the medical/developmental things. Not the minutia of how I parent. E.g., pedi asks if baby is sleeping, I say yes. End of story. Details are not important.
ETA: In our house, we all sleep better if we cosleep. So that's what we do. It makes for a happier household. As long as you are safe about how you do it and everyone in YOUR bed is in agreement, then that's all that really matters.