I'm against it. For one thing, there are a lot of kids that need homes, why shouldn't someone that cannot have children themselves adopt a child that is already here on this earth. Don't these kids deserve a chance.
Another reason I am against it, is because there always seems to be problems arising. You get attached to the child growing inside you, you wouldn't want to just give it away. It would be inhuman. There are a lot of emotions and feelings involved.
It's not fair to the children either, yours, nor the one that would come out of this. A child deserves to know, and be with, it's real family.
It's also a pretty weird situation for your husband to deal with you having another mans baby growing inside of you. Once you go through with it there is no turning back. This could ruin your perfect marriage, and family. You should not risk the happiness you have with your family.
It's nice that you want to share the happiness you have, but this is not a good healthy way to do it. There are all kinds of ways to help make this a better, happier world. Get involved with
existing families in your community to see how you can help. Get involved with organizations that help. Don't back yourself into a corner with something you may regret later. This isn't a productive way to go. Donate your extra time, and get your kids involved in some charitable work that helps people out in a good way. Maybe you should check out your local orphanage and see what you can do to help.
If you know someone that is in dire need to have a child of their own, direct them to an adoption center or orphanage. Here is a link for you to browse. http://www.orphanage.org/ There are so many children in need of a loving home.