Going to India - medical questions (vaccinations, etc)

We are Indian by origin but been in the US for ~30 years. Our last trip was 6 years ago. We will be visiting only Bombay and its suburbs. Of course we will be careful not to drink fluids outside, patronize street vendors etc. But we gathered up a list of potential immunizations/vaccinations we might need to take, and the cost for getting these done at a local travel clinic runs to around $700 for 3 people. A bit steep if you ask me

These include:
TDAP (tetanus, diptheria, acellular pertussis) - all in one
Hepatitis A/B
Malaria.


So am wondering:
a) which immus are essential, and which are overkill (if any)? We are two adults and one teen, all in good health, with various appropriate immus already in place, but the figure I refer to above is for the stuff we don't have yet.
b) For the ones we do need, where is a good place to get these (generally speaking, ie type of place).
c) As Indians know, this sort of thing would cost way less in India itself. Is it feasible to get all these arranged via the people we are visiting, and then get them done the day of arrival itself? I guess I am asking if that is ok timing-wise or too late.