From a child care point of view.
You won't be able to find child care that goes and picks your child up after 2 1/2 hours. They won't transport them there and then turn around and pick them up either if you go to work at 7am.
So before you can even consider the option of working during the week you have to face up to some facts.
You will have to take your pre-schooler our of pre-school and put them and the toddler both in child care full time.
If you work 7-3 5 days per week then you still might end up on weekends sometimes right? But in child care you have to pay for the whole week even if you don't work 2 of the weekdays, you'd be off 2 weekdays and work 5 days which would include Sat. and Sun.
So you'll still be paying a set amount for child care. Good thing though, if your center picks up school kids then they'll be able to do your kindergartner next year if they go to his school. Then you'll only pay for after school care if hubby gets the kids off to school on your early mornings.
What I did for a family is this.
I worked as their nanny, in their home, but I had full autonomy. I took the kids where I wanted to go, I took them anywhere. The zoo, the mall, choir practice, to the store, out to eat (I paid if it was my choice), and I was basically their surrogate mom. I cooked their lunch and picked up after them, that's all.
I got paid per load of laundry that "I" did at their request, I got paid for doing any cooking for their dinner, I got paid extra for any cleaning I did, etc....I got paid enough to have pocket money but not enough to call it a full time job unless I was doing a lot of household chores.
I was not tied down, I did not get gasoline paid to me, I did not get paid for a full day for the school kid that went half day, I did have a lot of fun with these kids. The mom was a professor of nursing and did have an 8-5 job.
Can I suggest that you wait until kiddo is in kindergarten to go to work full time weekdays only?
Do you have an advanced degree? Could you find work at a Jr. College level or Vo-Tech teaching nursing? It might not be as good money that you get doing nursing but it might weigh out with benefits and stuff. Once you were there for a few years you'd get tenure and have even more benefits too.