What to look for

I had posted previously about adopting a two yr old. Our bm's parents have been raising one of her children since birth ( adoption was hoped for ) . The child is now two and they have refused to care for him any longer. He is back with his birthmom who he does not know. We have been offered the chance to adopt him along with the baby that is due in feb. We are going out to meet them this weekend. We would want to make sure we are the best family for him and can give him the attention he needs. My worry is that with two older children 11,9 a 1 1/2 yr old and a new born if we would have the proper amount of time to bond with him and give him a complete sence of secruity. If he had no lasting tramatic bonding issues I think we could do it but there is no way to tell . Is there things to look for or to ask his bm about his personaliy that would tell us what personality he has, I know every child is different, I just want to do what is best for him. His bm said there are families at the agency she called I just dont want to be selfish if it would be best for him in a home with out so much comotion. Having three energetic children with a newborn on the way, if we get to spend time with him what should we look for in his personality that might give us an idea if we are the best place for him ? Thank you so much