First of all, congratulations on the wedding. Less than ideal circumstances, but still a wonderful occasion to celebrate the love you have with each other.
Secondly, I am so so sorry that this is the situation you are in. It's horrible. It's unfair and it's cruel. Nothing anyone can say will change that.
But you will survive. You will get through it. Even if it doesn't feel like it at times. It will be hard. So hard. But you will be OK, and your children will be OK.
One of my best friends lost her husband in an accident just a few months after they got married. They had one child in y5 at the time. She's three years on now, and while she is of course still grieving her husband, she's also living again, and her son is in high school and doing well.
She told me that all she could do in those early days was get through the day hour by hour. When she went to bed, she would tell herself 'I've managed to get through a day', and at the end of the week she would 'celebrate' getting through the week by buying herself a fancy coffee, a new book - just tiny things to remind herself she was surviving and even when it felt thr world was falling in, she was still there, still holding it up.
I don't know if that's any help, but i know it helped her.
Make sure you are looking after yourself as well. You've just had surgery and you matter. Reach out for support, don't worry about feeling cheeky to call in favours and ask for help. Schools often have a family support or liason officer that at the very least will be able ton signpost you to help and put measures in place to support thr children in school.
Sending you lots of love