So I'm going to be a bit practical and start a list but you don't have to do any of this tonight. In fact you shouldn't. All you need to do now is keep yourself and dd warm whilst you take the first steps adjusting to the shock. Have a hot drink if you can, eat if you're able but just keep warm and wait this first vile shock out. Then:
Short term stuff to do
First ensure people who need to know are told. This is when you find somebody, friend, mum, whoever and you tell them who needs to know and they do it. Don't feel you have to tell people yourself.
Include any school or employers involved
Monday onwards:
The hospital will prepare the death certificate. You don't need to get it immediately but you will need it soon to organise a funeral and for Many other admin tasks. They should have a bereavement link service you can speak to. You will then need an appointment at the registry office. Take your husbands NI number and you can use the tell us once service which contacts a lot of agencies and is helpful. Get at least four copies because lots of places will want an original and you don't want to wait for them to come back in the post. You have to pay for extra copies.
Contact a funeral director. (They may be available over the weekend for limited contact I think) They are very kind helpful people who are used to dazed people knowing nothing. Ask friends for recommendations.
Find the Will and contact his executors which may well be you anyway. If there isn't one don't panic, as his wife you are in charge.
Money - if your money is in a joint account it still works. If most of your money was in his accounts ring his bank and explain. When you have the death certificate they should be able to help. You can get an overdraft added to your account if needed and the bank can manage matters so stuff doesn't bounce back.
Arrange what you want to say good bye. You don't have to have a formal funeral or if you like you can have a horse drawn hearse and full choir. It's up to you. Think about what he liked, talk to his friends and ask on here for tips. Your funeral director will also help.
Think about clothes and hair/make up. It's not shallow, it's important to feel at your best and you won't believe me now but it will help. You want clothes that are warm, comfortable and fabulous. Get whatever treatments you want and can afford.
Medium term
Work out the money, there are likely pensions etc. Find a helpful friend and take it slowly, lots of advice online and institutions have bereavement teams to help people like you. Expect it to take at least six months, quicker is then a bonus.
Sort out what you want to keep and what you want others to have. There is no rush for this, sone people will offer to sort it out for you. Don't let them. Working through his belongings and wishes will make you cry but it's a key part of grieving. own it. You'll be glad you do. But don't do this yet. Keep living the life you share.
I'm so sorry Op. wishing you peace.