I would be saying to my mother-why on earth did you saddle me with a name that has nothing to do with me-other than you lived with a man of that name for a short time?
By the time the child is old enough to question and understand this, they will have known that their mother and siblings have the same surname for as long as they have been alive, so it will be completely normal for them. I highly doubt they will feel 'saddled' with a name that they share with their mother and siblings. They may feel more 'saddled' if OP splits from her DP and they are the only one in the household with a different name!
Also - OP has had this name for 10 years, 1/3 of her life. By the time the child starts to question it it will be more like 20 years or even longer - so more than half her life. Hardly a flash in the pan. I think she has the right to call the name hers.
Tennytiny you really are remarkably slow on the uptake. You don't have to ask a man (or anyone else of that surname) if you are allowed to give a child his surname. How do you imagine that would work? I'm Ms Smith, I want to call my baby Baby Jones, does the registrar have to ask every single male Jones in the UK if he minds me using the name? Come on - bit of common sense please!
It's funny how threatening people seem to find it when a woman decides she's going to a) go against the status quo and b) make a choice for herself! I also find it incomprehensible that women are saying that a name you took on marriage, that you have been known by for ten years, is only 'borrowed'. Should a woman 'give it back' if she divorces after 40 or 50 years of marriage? Are womens' identities so unimportant that their name is only theirs as long as they remain belonging to the man who properly owns the name?
This is why I would never change my name 