advice needed please

Jada
This is my most recent sono , i was about 6w5d with my twins. I am 10w1d as of now. I have a 6 year old son already. I need some advice on how to get my son comfortable with the idea of being a big brother. He has trouble understanding mommy cant rough house right now and he gets sad or anytime i bring up the babies he says things like where are they going to go because we already have him, he gets upset when we shop for the babies and asks why do they need that why cant we just get him things. Also i am trying extremely hard to stop smoking and although I have slowed down dramatically i find myself sneaking to the store for a cigarette every now and then. My partner tries to help with all of this but we are both stumped. Any suggestions?