Need Advice.......................................

Ok so my boyfriend and I are expecting our first child together. Awesome and exciting right. Well I have a daughter from a previous relationship/marriage that I have 50/50 custody of, and my boyfriend has 2 girls from a previous relationship as well. He has shared custody of his girls has well but his oldest was taken from his ex while she was pregnant with their second(did not know the second was his until mid December), so he has to go through the county to see his oldest and his ex refuses to let him see the baby at all. Well we are looking at getting a place of our own and one big enough for us and all 4 kids(that MY plan anyways). Is it bad of me to want to prepare a room for my daughter(3 almost 4) and his oldest daughter (1 almost 2), and then make a nursery for his youngest(she was just born the beginning of November) and the baby we expecting who is due in August? Just to show the social workers he has to work with that we are prepared to have both of his kid as well as my daughter and the baby we are expecting. Or am I over stepping my bounds? I feel like sometimes I'm more concerned with proving that he is a good parent and has a stable home for his girls then he is. Not gonna lie I fell like maybe he doesn't care and is just ready to give up on ever seeing his girls as their mother is a complete psycho. And I can say that because I personally know her and have seen first hand how crazy and manipulative she is. Just really confused right now.