Oh goodness, I am so sorry. I’ve been through a similar experience and I will share what worked for me. Appreciate that you are not me of course!
It is quite normal for your mind to go over recent events over and over again, but do seek help from your GP if it’s distressing you or preventing you from sleeping. Mine gave me a few days worth of diazepam to help in the immediate aftermath and I found that it was beneficial, then followed up later to see how I was doing. I found that when the sh*t hits the fan, that the services were good and pretty joined up. Hoping it will be the same for you.
There was a six week wait for counseling on the NHS at the time (but it could be more immediate if you can pay). I am fine now, although I struggled to imagine getting to that point immediately after it had happened. Although the experience will never leave me, it doesn’t have such an effect now and I’m able to focus on the good times we had together.
For the children I tried to keep their routines going as best I could. Routine did, despite the sudden change to their lives give us all some sense of stability. For me this was pre covid so they went to school as usual and whilst they were out a relative stayed with me, helped with practicalities and took me out in the car for walks as a distraction at other times. They were a godsend! Do ask for help with meals and let people know what the kids enjoy eating too if they don’t like casseroles!.
Do let the school know what happened as soon as you can and they should offer support. Ours was really good and offered child mental health support, and the staff were lovely, keeping me up to date with how they were coping whilst at school.
If you’re home schooling I appreciate keeping the routine with the children might be more challenging. Maybe a relative or friend who the children love spending time with could take them out if you need a bit of space to make some phone calls.
Please be gentle with yourself, you are probably traumatized, so be open to letting people you trust share the burden of practical things. You will probably want to let some people know what has happened directly, and I’d advise asking them if they would be willing to tell others they are connected to who know you and your husband to avoid having to tell people again and again and deal with their reactions.
Sending love. 
Please pop back to this thread if you have any specific questions or just need a hand hold.