You will only be able to get your children into your school if they fulfill the admissions criteria and usually that will mean you need to leave near enough. There are advantages and disadvantages to them attending the same school as the one you teach in.
Usually you will need some sort of morning childcare anyway as you often need the mornings to set up and meet with colleagues. Some schools do staff meeting in the morning and it's a key time to meet with support staff or even have a chat with a working parent. Not many primary school teachers are on site later than about 8.20am.
It would be unlikely that you are able to attend your children's plays/ sports days if they are at a different school. I have heard of people occasionally being granted unpaid leave or a kind headteacher letting someone pop off for a couple of hours and making temporary staff arrangements but if you work fulltime and have a class it's extremely hard.
How soon you can leave depends a bit on your Key Stage. I would say that you might manage a 4pm departure on 1 or perhaps 2 days of the week (with work to do at home later). Usually you have one day of staff meeting ending around 5pm. One day of a Key Stage meeting or planning meeting. 1-2 days of meeting with another colleague e.g. the SENCO to do IEPs, your mentor if you are an NQT, a senior manager who has done an observation and is giving feedback, a classroom assistant or someone you are team-teaching with. And then perhaps one evening when you need more time to get resources together e.g. a good rummage in topic cupboards, making resources you can't take home easily or time to put up a display.
I know I am sounding a bit negative but I think it's important to know combining teaching and family life isn't as easy as it might appear. You also need to find time at home to do marking and preparation and initially that could mean 1-2 hours every night and a few hours at the weekend.
I was a teacher for 9 years and I LOVED it. Primary teaching is a magic job but it is bloody hardwork. You do need to find some great childcare though and expect a long day. When you get more experienced it is easier to work more quickly but even a more experienced teacher can do a 10 hr day without breaking a sweat. The holidays certainly help though.