Can I ask if you have a partner to help you?
Its a big job you are asking of yourself to work fulltime while your children are that age, but it can work. I think you have to learn that you can't be the perfect employee the perfect Mum and the perfect housewife at the same time something has to go, I think its the housewife because the precious time you spend trying to keep on top of all the housework is time that you need to spend with your children.
When you get your job invest in a few time saving devices, things that will make your life easier at home,Big freezer for storing ready made meals,even now though I don't have any children at home I never make one of anything, if its spaghetti bolognese I make enough for three meals and freeze it, always have an ongoing menu so that you know when you leave for work in the morning what you are going to have for tea that night, a slow cooker is a great investment, just chuck everything in and leave it to simmer all day. You probably do this anyway but wash every single day, never let it pile up, hang it on a dryer over night it will dry fold it up in the morning, and my last tip is clean one room a day properly, keep on top of your kichen and your dirty washing and you will get through.
Well thats my advice, and never be afraid to ask for help, don't feel guilty, I still feel guilty now from years ago when I worked full time but I did not have anyone to give me advice and I tried to be everything to everyone and I can't, thats something I am still trying to deal with now.
Good luck in your new venture