I do understand you are worried, the logistics and practicality of it is daunting right now.
all I can say is that you will need a lot of help, paid or otherwise and you must organize this by the 3rd trimester.
school run - the best thing would be if someone could do this for you or stay home with others while you are out.
this would be my starting point as it has to be dealt with.
so questions you need to ask yourself - how far is the school and can you walk there in 30- 40 mins tops? can some of the kids walk it or will they be able to do so in Sept or after baby's born?
go for a walk and time how long it takes to get there with the children's speed.
I find walking much easier sometimes, parking and in and out of the car can be a nightmare.
is there a school bus available?
if parking is not a problem it might be easier to drive.
what pushchair/s do you have/will you need? can you borrow a triple one if needed or get a cheap one?
then onto the next subject - time management.
what would be a reasonable morning routine? how long would that take to get them ready? can the older ones dress themselves?
and so on.
if you break it down in to small pieces, and think it through step by step (write a list) you'll find out what it is that you need, want or can't do. that will help you find solutions and answers.
however scary, once you start figuring out you'll start to feel better, I promise you.
I wish we could chat about this on the phone! 