You need to make your life as simple as possible and, depending on finances, buy in as much help as possible. Your Partner also needs to step up and take on his share of the responsibilities - you can' the default parent, default home organiser AND work full time. Make sure you and your DP are on the same page regarding time off for emergency sick care, school plays etc etc.
I hate meal planning, but it is a much smarter way to work as I can shop in advance and I build in planning meals that are easier/quicker on days that I need them and I don't have to think about food at all during the day. Similarly, meal planning allows you to plan for whatever meal preparation your DP is doing without it leading to a crisis and stress every day.
If you can, buy additional school uniform and PE kit. This allow you to simply do one giant load of school uniform and PE kit at the weekend, removing the need for daily monitoring and checking.
do not allow your children to get into the habit of packed lunch. School lunches all the way I did not learn this lesson plus I have fussy children with intolerances. It is a pain in the ass
Make friends with other parents on the school run, particularly ones who are the parents of your children's friends. Then, over time, build in optionality for emergency support. very very importantly this must be a two way thing - so you take Janet to ballet on Saturday and Janet's mum collects your youngest on a Thursday. Ad hoc or regular.
Do not get a pet.