Well, mama, I will say this. To make it work, you will have to super-duper organized and accept that you will never have any time for yourself, and very little for you and your DH (which means that while he's accepting of the plan now, he may start to change his mind if he gets disgruntled, IYKWIM). I spent my first two years of HSing as a WFH mom (also for a global corp., they were very kind and very flexible), and we got very little schooling done. If I were very, extremely organized and not a total introvert, I think I could have made have made it work, but I'm not either of those things
I would not put the school area in your office, because it makes it very hard to separate the two things, and sometimes they really need to be separated, especially when you have conference calls and small children. The thing that helped me the most was to make a detailed (half-hour increments) daily/weekly schedule so that I could see where I was going to need to be and when, and whether there was truly enough work and school time built in or whether I was imagining there was.
You'll also need a very reliable caregiver who will be there when they say they will and will do the things they say they will. My mom was here for us for years so I could work from home with the kids, and while she was wonderful, she was also not very reliable in terms of when she'd be here, so I'd end up telling the kids, "Mimi will do that with you when she gets here, Mimi will do that with you when she gets here, Mimi will do that with you when she gets here..." and then finally I'd end up starting something with them myself, only to have it take me extra time to extricate myself from the activity when she did finally arrive, etc.
You'll need to be super-disciplined with yourself, or work time will bleed all over home/school-time and vice versa, and you'll find yourself burning the candle at both ends to get everything done, and then YOU'RE the one who pays.
It would also help to automate as many processes in your home as you can--meal plans that repeat every few weeks, a cleaning schedule that you can rely on and that dovetails with your work/school schedule, a recurring grocery purchasing list, etc.
Basically, the bottom line is that if you're working and HSing two kids, you need to have total control over every minute and every detail, or the edges start to pull loose. It's a LOT to pack into one week, you know? And while it seems like it would be easier with smaller children, the fact is that while they have less actual schoolwork to do, they still need that time from you--lingering bedtimes, messy activities, trips to the park and library and playdates, etc., buttery popcorn and movie nights, etc.
Ultimately, I left my job eight weeks ago, because I felt like I was doing all my jobs (mom, teacher, wife, employee, myself) horribly, and was not coping well at all. BUT, as I said, my personality contributed a great deal to that (as did the fact that I was not thrilled with my job anymore). I believe it can work, and I know some moms who do manage it, but they work out of the home and have another parent home splitting the shift with them (e.g., working nursing shifts over a three-day weekend, or working from 5 a.m. to noon, things like that).
I don't want to freak you out! I've just come through exactly what you're asking about, though, so I have some relatively fresh insight into the situation. If you have more specific questions or want to chat about it, feel free to PM me or ask here. Like I said, I think it can be done if you have the right kind of help/partner/personality/kids, and I'm happy to share my tools and experience if it will help you. Good luck!
ETA: Drat! I just typed a whole extra bunch of stuff and then lost it. Let me 'splain. No, there is too much. Let me sum up... (heh!)
I just re-read your OP, and I may have given you way more than you need to hear
If you've been HSing and coping all this time and just need coverage for the time that the pre-K/K would have covered you, then you'll probably be fine. If I were you, I'd look for a helper (MIL or otherwise) or a family daycare situation. Lots of HSers take in kids to make extra money so one parent can be home, so you might even be able to find a HSing family to help you cover that time. I wouldn't try to, say, have the kids in the next room while you try to do corporate conference calls. IME, kids have a tendency to "see mommy, need mommy," no matter what you tell them about not fighting or keeping the door closed.
Anyway, that's my $1.02, FWIW to you. I hope you can make it work!
