I will pick up the following things you say Auntpolly:
I work in a financial institution in which motherhood is viewed as a weakness.
I would want to be back in work when DS gets to school age.
I've had 2 chest infections and shingles since the start of year.
[my skills] are very specific to the operating platform of my company.
This makes me feel that if you leave the company then you are likely not to be able to get your job back again, with that company or another... as your skills are very specific. So what would you see yourself doing when DS gets to school age? Would you really want to sit on the checkout at a supermarket? Would the supermarket even employ you - as on paper you will have quals and skills they may feel are far beyond the job.
Given recent health, does your company offer any opportunity to take unpaid time off, such as a career break? While that may result in your position at work being lower when you return, it does keep the job open to you. Possibly something to look into with HR Dept.
Also look at long-term sick leave... if your health is suffering it may be in your companies interest for you to have a short break.
I would try to avoid both those possible options though, as I suspect that given the attitude towards motherhood, they may have similar attitudes to people who take anytime off for whatever reason.
Think really carefully about if you really want to leave your career. It is what you know, what you are good at, it may be where your friends are.
End of the day you need to do what will make you happy. I'm far happier now that I'm earning less money than I did in the past, though I work more hours now... but I'm doing work I like. It will never buy me a house though... and I don't have dependants so I'm only needing to support myself.
Are you spending weekends as quality time as a family? Or are you spending weekends doing household chores? If it's chores - then I agree with those who have said that it may be best to look at getting household help, rather than leave your job.
You may also want to look at childcare again... seems a little daft to have two forms of childcare, when the childminder could probably have both your children (if childminder has the childcare places available). A childminder can also take children to/from school, whereas nurseries often don't do that - thus with a childminder you will be having a longer term commitment.
I'm not in your situation so I can't know what it's like. However in this current economic climate and political situation I would be very hesitant about leaving a job.
I also agree with StarExpat... that being a SAHM may be very exhausting. I work with children in a family home... so thus am sort of like a part-time (40 hours a week) SAHM. It is exhausting at times caring for two young children. You still have the same difficulties in getting them out of the door... it's just at a slightly different time as takes shorter time to get to where they need to be - school for example. Once oldest is at school you then have a toddler to entertain all day, a toddler who is constantly demanding attention, who is throwing tantrums at random points, having to get the washing done - yet toddler knows how to change the settings on the machine, etc.