In the end, I didn't do it, but certainly looked into HE in some depth. I'd say it's pretty well do-able if you've got the time and initiative, able to do plenty of research and personally capable of doing the work you expect them to do, i.e. an average standard of education yourself. There are loads of online support groups, online chats, Facebook groups, etc etc which are full of brilliant advice from people who are doing it.
Don't think of having to spend a full "school day" sat at the dining room table. When you break it down, the kids actually spend only a small amount of time actually "working", when you take into account the registrations, assemblies, breaks, PE time, art/singing/dancing time, etc. You can spend quite a lot of the day doing "fun" things like arts & crafts, physical activities even just kicking or throwing a ball in the garden, or playing with tennis rackets etc, or going for a walk, etc.
At their age, you'd be doing fine (probably as much as they get in school) if you did an hour "formal" work in the morning, an hour in the afternoon, and then a reading "hour" in the evening. By that, I mean "proper" work, such as worksheets, reading a simple text book, etc. You can then fill in with another hour or two maybe watching factual TV programs, BBC bytesize, child-targetted documentaries, even You tube videos. The last thing you want to be doing is forcing them to formally sit at a table/desk for any longer than say 2 or 3 hours per day, and you're be better doing it in half hour chunks with some other learning activity inbetween (such as a BBC bytesize program to watch). Also don't forget that lots of museums etc are free entry and even those they may not be particularly interested in could still be a fun day out and educational to broaden their knowledge and view of the world, such as the national railway museum, science museum, natural history museum, and you could repeat visits after a few years - as they get older, they learn different things.
Obviously you need to research the curriculum to ensure you're broadly working in line with their school peer group based on age, etc., so that you're broadly covering the same topics, they're working broadly to average levels as regards literacy and numeracy, etc. You don't want them to be getting behind by you thinking they're doing ok but in reality they're a year or two behind their peer group!
Secondary years is a different kettle of fish, and will be particularly problematic when one is primary age and the other is secondary age. I presume your plan would be to send them to secondary schools as normal and just do HE for the primary years?? If not, then secondary years are a lot harder to do HE, especially if you were aiming for them doing GCSEs (and then A levels) at the usual ages as you're likely to struggle after the first couple of years when you start having to "teach" the GCSE subjects, not due to time (as even at secondary, a lot of the school day is pretty much wasted), but the complexity, and you need to know the subject yourself to be able to "teach" it to someone else. Although I did read quite a few posters on HE forums saying they were "learning together" with their child which seemed to work well, i.e. bouncing ideas of each other, struggling together to understand specific concepts, etc which seemed to improve the dynamic rather than the more "traditional" teacher and pupil roles!
I know someone who did it right from the start, never sent her kids to even primary school, one is current doing GCSEs and the other is doing A levels. She's never looked back and never regretted it, and from what she says, her kids have done well out of it, both aiming for Uni.
You've loads to think about and it's nothing to go into lightly, but if you've a pretty decent education yourself, then I think your own time and inclination, enthusiasm, etc., is more important than what you may think are practical difficulties such as them not having desks!