I am a teacher, and this is what I would do.
Don't try to recreate school, but do have some sort of structure
Stick to a routine of some sort, it is much easier to enforce.
Decide what 'get up' time will be, and wake them up and get the day started at the same time. In the long run, this will save your sanity.
have 'school time' if they have school work to do, mine are secondary, so probably 9-12. But it might only be 9-10!
As far as possible, use stuff set by school. As far as possible, get them to work at it independently. If school haven't set anything, look at the sites on the mn thread and do 20 minutes eahc on 3 different sites, plus 20 minutes reading (younger children can also read aloud to older ones)
Timetable in 'play' time, with a long list of suggestions which are not screens (lego, playdough, art project, monopoly, poker....)
Play time is your best shot at getting your own work done. Be ruthless, you may not under any circumstances disturb me. If you are bored go to the next item on the list. Get this set as a practice, it will be hard for the first few days, but will improve as they settle into routine and get used to the idea that for certain times, you are not available.
Play can get better as they get used to the idea of no school. Drop ideas in casually, eg building a lego city, making road/rail that connect room to room, building some landscape for it. Whatever works for your kids.
Play can also be outside, frisbee, football, basketball, teaching the dog tricks, tree climbing, whatever is available.
Then also get out of the house. Go for a walk if you can safely. Set up a daily competition - 10 shuttle runs to the back fence and back. next day 15, then 20 or whatever.
Then towards the end of the day, allow them screens. playstation, films, dvd, phone. This is your next key block of work time. they will settle better with screens having been denied them until now. Again, no interruptions unless emergency.
This may seem harsh, but it is only for a limited time, and actually, with older kids, it is teaching them to work out their problems for themselves. When they come with a squabble, don;t sort it, say - I wil sort it at 4 o clock, until then you can choose to be in different rooms, or you can negotiate to solve it.
bedtime remains same as school day. This is your last block of work time, after they have gone to bed.
Hope that helps, it does settle in over time, the first few days everyone is going to be all over the shop