I work full time, though my DDs are older than yours (4 and 5).
During term time one of us drops the DDs at school at 8am, in the holidays our nanny starts at 8am. DH is home between 6:30 and 7pm. I'm usually home later, sometimes much later (solicitor in the city - antisocial hours).
I agree with lower your standards. If you can't lower them you have to get help - cleaner, ironing service, whatever. We have a cleaner.
Batch cooking is a huge help. Also find stuff that's quick and easy to cook. DH is a whizz with bangers and peas, pork chops and peas, gammon and peas... And the occasional ready meal/take away never killed anyone.
Always pack stuff the night before - yours and the DCs.
Automate as much as you can so you don't spend the weekends on admin. We have milk delivered at home, and you can top up with small essentials like bread (if you remember before 9pm). Online shopping is also great. Now the DDs are at school their newsletters etc are emailed which is really useful. I often use the train journey to/from work for all the home admin - emailing friends to arrange playdates, booking into swimming lessons etc.
It's useful to have a whiteboard/similar up somewhere to write down those things you will forget - from food as you run out of it to extra things the DDs need for school that week.
It helps to learn to shut stuff off in your head - so when you're working you work and when you're at home you turn work off. Took me ages to learn to do that, and the constant blackberry access didn't help. But when I am with the DDs now on week nights, I am 100% focused on reading stories, taking to them etc.
Every so often things will run off the rails - sick child keeping you up all night when you have lots of deadlines etc. When that happens and you are feeling at the end of your tether, take time to be kind to yourself. Even if it's just a lie in one Saturday morning or taking a few hours to read your book in a coffee shop.
DO NOT VOLUNTEER TO BE CLASS REP!! That is my massive learning curve from this past year. By all means sign up to help at an event or two but having the responsibility all year is hectic.
Make space for you and your DH too. When our DDs were little and quite frankly neither of us felt like tarting up and going out, one of us would cook on a Friday or Saturday night and make something special/different and we'd eat at the table, no TV allowed. And yes, it was often interrupted with trying to get one of the DDs to sleep etc but it was a good way for us to unwind together.
It is so much easier now my DDs are older, I'll be honest. And although it is pretty full on, I actually quite enjoy working full time. You do land up having to be super organised, but perhaps that's not a bad thing!