Hi there. This post is quite old now, my daughter is 2 next week! Her surgery went well & she only has a tiny scar & a slight bump on her hand now, so you wouldn't know she'd ever had an extra thumb!
I can understand your concerns about the extra toes affecting your daughter's walking, but if she has the operation at around 12 months old it might not matter since a lot of babies don't walk until after then anyway. In regards to her being teased.. my daughter went to nursery for a while before she had her thumb removed & none of the other children treated her any differently. If your daughter was with kids her own age (or even a little bit older) they wouldn't realise there was anything different about her because they'd be too young to understand.
Good luck, I hope everything goes well for you & your little girl.