I'm a childminder, and until I went on maternity leave I was looking after 2 toddlers at home all day. One was my own son. They did the same activities, got the same amount of attention and cuddles, created the same amount of cooking, tidying and washing up etc. But one was my "job"and the other one wasn't.
I find the whole sahm vs wohm argument bizarre really. Surely our grandmothers fought for women's rights so that we can have CHOICE not so that we get backed into another corner full of society's culturally determined expectations.
I am basically a sahm because I want to be, and because DH and I both feel that is the best thing for our family. I have not inherited wealth!!! I don't give a stuff about having a career, and I trust DH to provide for us financially in the same way he trusts me to take care of the kids and manage the (very tight) household budget. If having a career was important to me, I would work outside of the home and find good quality childcare. But I love working with children and I prefer to be with my own children rather than leave them with somebody else.
To me, feminism does not mean that I have to let somebody else look after my kids while I go and work in a call centre. It means that what I do at home should be valued, and that if I was in employment I should get the same pay and benefits as men doing the same work. Also that if it was DH at home with the kids all day, he would not be looked down on for doing "women's work" - looking after children in a home environment is an important job and should be valued by society.
So there! 
OP, I have never found a good snappy answer to the "when are you going back to work?" question. I also loathe being told that I am "lucky" to be able to stay at home... Some of the people who tell me they couldn't afford not to work go on foreign holidays and have two cars etc. We are always skint, but have made a carefully thought through and perfectly valid lifestyle choice.