Hi! Your children are so cute!
A lot of new information has been learned in recent years about vascular birthmarks and birthmarks in general I would suggest you go see a specialist and see what they have to say...maybe start with a dermatologist. They may know more now about why it grew back and if it will grow back again if removed. Do you have a good dermatologist near you? You can also go to the Find a Doctor link above. That might be helpful to you.