I don't think wanting to be a SAHP or wanting to change your name is unfeminist OP, but I agree with what subsequent posters have said about "choice feminism" because IME, this is often attributed to behaviours that actually harm women. It frustrates me that "choosing" to be a lap dancer or escort is repackaged as an empowering choice for women, when it merely serves to objectify us.
Lots of men want to be SAHPs too, but you are right that economics dictate that for many families, they simply cannot survive on one wage alone.
I post most frequently on the Relationships board and I see thread after thread from women who lost their financial independence after having DCs and now feel trapped in relationships they no longer want - and this is likely to get worse with the coalition government's proposals that are being dressed up as protecting the "family", when in reality they are creating obstacles to women leaving abusive relationships.
I admit that this often makes me wish that more women retained their careers and opportunities and therefore the power to live independently and that when having discussions about who is going to be the SAHP, more thought was given to the primary carer's employment opportunities if the relationship ends, or when the SAHP decides to return to work. It puzzles me why so often it is assumed that the primary carer for children will be their mother, especially when her earning power is higher and/or her partner would also like that choice.
Depending on prior qualifications and skills, men returning to the workplace after SAH parenthood are still more likely to secure a job and earn more than their female partners.
As a working parent, I have frequently had irritating questions about who is caring for my children, when my husband received no such enquiries. Likewise, especially when the DCs were younger, if I went away for the weekend with friends, I would get lots of questions about who looked after the DCs and most irritatingly, lots of "Ooh, isn't he good?" when I replied that they were being cared for by their father 
. As you can imagine, my H has never once had the same questions or observations that I was good, when he did the same. I might add, that most of these "enquiries and observations" I faced, were from other women...
On the flip side, my daily rate is considerably higher than my H's and if I don't go to work, I don't get paid. If the DCs are ever sick on one of my working days, my H will always be the one to take a day's leave. Some of his same-age male colleagues only seem to understand this in economic terms i.e. that it makes financial sense for my H to take time off, rather than it being the norm for parents to share the "sick kids" days. My H now observes that our way of doing things is much more common amongst his younger male colleagues, so maybe there's hope!.
My perspective on your situation is that like many men, you are working out of necessity. That isn't unfeminist at all, just as a man who wants to be a SAHP and begrudges the time he has to spend away from his family, isn't less of a man.