Empty the house, literally. If they break it, dont replace it. Lock your stuff away if needs. Bedrooms need to be bearest minimum in terms of stuff, furniture and wall hangings. You need a low sensory low stimulation environment, no pictures. One or two favourite toys and that's it.
In the long run you probably need a proper "sensory room" (dark black out curtains, quiet with slowly moving lights different textures). Some people have success with a black out tent as a cheap alternative, yours I think are a way off a tent being sensible. Some people have a shed, in the uk there are charities that can fund, not sure about canada
You want anything that encourages healthy sensory physical input, trampolines, spinning (eg budget ideal and hanging (eg monkey bars in the garden or the pull up bars that hang from doorways in the house). You will probably find they pick one or two of these inputs more than others, you might already have noticed they bounce or spin a lot.
You need to be (up early) walking or scooting for a good hour a day in the morning and the same again in the afternoon. Ideally probably also lunchtime for the time being until they settle down a bit. If they can rollarskate so much the better, you want any activity that is harder for them than you. Play park morning and afternoon if possible. You will be exhausted initially but it will get easier. Weekends need to be long walks, long bike rides and robust play parks. In the uk zoo memberships can be good if the zoo is particularly expansive. Swimming especially at a competative style club can also be good. Some kind of telly based exercise like the kids section of les mills on demand can also be good especially when you're at home and your attention needs to be elsewhere.
No time outs. Leaving them alone for a time out is not a good plan. But no long talks either, they are too wound up to listen and cant listen to you properly until they've calmed down a bit. No grounding, they need to be out and doing as much physically as possible.
Cultivate I'm not interested in what dad does here we do this. Stick to it like a broken record. If you are telling off use less words not more, never explain why unless they ask later when calmer. Even then often no is a complete sentence.
No TVs or computers two hours before bedtime, audiobooks ok reading ok. No ticktock (very very poor for concentration and adhd). You tube on ban for now, vet you tube channels before they are reintroduced. Nothing with whizzy graphics and speedy editing cuts No real time computer games you cant pause (eg fortnight). that needs to be a long term hard rule, as they require too much emotional investment. run visual timers like a kitchen timer or a specific hour glass for everything including screen time the time the walk will take etc. In your case I would only allow tablets when you are working if they have walked.
Sleep sounds/music at bedtime and any time they are meant to be asleep. Try different types, some work for some people and not at all for others.
Sit down once a week to board games. Start with games that are quick to learn, chance based and short in length so they require low emotional investment and when they lose they've got another chance. Something like pass the pigs, jenga (if coordination is not an issue) or sushi go. Slowly introduce longer games. Nothing that hypes your specific kids up.
You might find running a marble jar works. Marble in for anything they do good. They use that to earn whatever they want (a toy back, half hour on the computer). Screen time us good because it doesn't cost you anything) Actively look for good things they do to give you an excuse to add marbles. At the end of the day Empty the marbles at the end of the day for the reward eg screen time tomorrow. When they get the idea that marbles are good start taking out marbles for bad behaviour. At the start limit it to really bad behaviour but by the end of the a week or so as the behaviour improves you slowly raise your expectations, it has to be better behaviour to earn the marbles and not as bad to loose them. Eventually introduce bigger rewards they have to save their marbles for. It allows for hands off discipline.
Yy to the diet and e numbers and sugar. No hidden sugars likefruit sweetcorn and fruit juices. Only added sugar squash, water or milk to drink.
You will probably find eventually they dont need everything and it will take some time for it all to kick in. Give yourself a deadline of a month. At the end of the month sit yourself down, recognise any progress you have made (and it may be slow but you will have) and assess what has and hasnt worked. Expect regression at any points of stress, growth change etc. Back to basics start again.
It can get better