It'll be fine, it really will. For now, prioritise kids, dh, work and you - dropping out of any other things you do for a bit so you can just concentrate on getting the essentials going smoothly will help your sanity.
Meal plan for a couple of months so you and dh both know what is to be done for tea, and you aren't fridge rummaging.
Buy a load of birthday cards so you aren't doing emergency buys. Pick up Book People book bundles and toys on offer so you have a party stash
If your dh doesn't do things like you would have, don't stress unless it makes a big difference. After all, if he chooses not to tidy in the day, but do it all in the evening, thats fine. If the kids aren't dressed as you would have - no biggy. And talk - thats the most important thing you can do.
I went back to work ft when ds was 4.5 months old, and dh works ft too, so we've just always made it work somehow with no family help. We do have a cleaner 3 hours a week, and she also does the odd bit of babysitting, but thats it.
Oh, and the family organiser - we put everything in our phone calendars, and theres a big whiteboard in the kitchen for this weeks events. Then your phone reminds you, plus you can chat about the week in advance. I put all the details of parties in the phone calendar too, like phone no, venue etc, then theres no issue of losing th invite. Do it as soon as you get things. An organiser book would never be looked at here