Anne, I'm assuming that since your son has it too, it is her aortic valve? How is her health otherwise? If it is her aortic valve, one option to consider is percutaneous replacement of that valve, unless the one she has now is too small which may make that not possible. The type of valve she received would most certainly be in her surgical notes. Did she have her original surgery at the Mayo, if so, they typically send out copies of all those notes after each visit/hospital stay. Others on here are more knowledgeable than me on this, but I didn't realize that a valve being too small could cause it to fail early, I just thought it could cause other issues.
As for your son, there really is no telling when he will need surgery, and depending on his age at the time, it may be best to consider a mechanical valve for him so he doesn't have to go through numerous surgeries in his lifetime.
Kim