Getting baby ready for another baby!

Hi! I have a 6 month old son and I just found out I'm pregnant with my second. Very early pregnancy, like 4 weeks, but I was wondering how other people got their young child ready for another baby coming into the family. He is constantly being over coddled by my monster in law even if we tell her not to. She will ignore our instructions and now my son freaks out if he is not held ALL THE TIME! By over coddling I mean never putting him down. Not even to roll around on the floor which his pediatrician wants him to do to build up his core so he can sit on his own. We told her what his pediatrician said and she called us "abusive" and "stupid parents" for wanting him to roll around our CLEAN floor. So now I'm worried that he'll be constantly crying because he won't be getting all the attention he has now with the new baby.