My DH works long hours (not home whilst DCs are awake Mon-Fri) and I've been both a working-mum and SAHM with young DCs.
Regarding food my tactic has always been to eat my own main (cooked) meal at lunchtime when child-free, even if it's just a baked potato at your desk, and then you always have the option of something really easy like soup or a sandwich for you and DCs at dinner time. And the odd ready meal isn't the end of the world, really. Or buy some fresh tortellini which cooks in a couple of minutes and is easy finger food for your DC.
Also, bath time isn't compulsory. My DCs have eczema and on GP advice only bathe every few days. That certainly makes bedtime easier!
Go with the flow if you have to. Inevitably you will have a day when you don't have the energy to argue. Pick your battles.
Finally, get some early nights. The temptation to stay up late with a glass of wine and watch trashy TV will get to you one night, I'm sure, but try to get some sleep in the bank.
Good luck!
(Oh, and when your DH does come back, make sure he is booked in for a big Daddy-time session so that you can slope off for a lie-in and a hot bath.)