My daughter had a "dangling" thumb when she was born that was removed shortly thereafter. We had a policization done on her index finger (making it a thumb) when she was 14 months old. It is important to have the BEST surgeon do this.
I don't regret having it done as she uses it well, but even though we had the best hand surgeon in Denver, it was not done perfectly. When she was 9 I took her to an AMAZING surgeon named Dr Scott Kozin to have a tune-up. Dr Kozin is at the Shriner's hospital in Philadelphia and he specializes in childrens' hands. The Shriner's hospital is completely free to any child that needs it and it doesn't matter if you have insurance or not. I would suggest that you contact Dr. Kozin (find the info on the web or email me and I will give it to you) before you continue.
My daughter has a rare genetic disorder and the thumb thing is a common anomaly. Have doctors considered and tested your sons for any special disorders as thumb malformations commonly indicate such a thing. Also, knowing that you have 4 precious angels in heaven it really makes me wonder!
Please let me know if you need any more information as doctors commonly miss these "orphan diseases" and I don't want you to miss something that could help your sons.
Typically infants do not receive surgery on their hands until they are over a year because the size can make a difference in the success of the surgery.
I will be thinking of you all,
L.