My dad's spreadsheet lists in the columns the companies we need to deal with, the issue they relate to, account number where relevant, details of how much DH paid or was paid, the contact person and phone number, date we contacted them, comments
The companies/ issues we have thought of include: apple for DC's ipod that he had the pin for, amazon prime for the family account for shopping and tv that he paid for, his allotment, bereavement support allowance, business bank accounts, car (I can't drive so we need to value it, find the log book, sell it, work out if he was still paying off a loan for it as we hadn't had it long), car insurance, car tax, charities he donated to or ones who send him letters that need to be contacted to remove him from the mailing list, child benefit, children's savings accounts that are in his name, council tax (you will get a discount for being the only adult in the household when you inform them), credit cards, bank account (we went to his bank first and they have temporarily paused the account so money won't go out, then it will be sorted properly once I take in the death certificate, I don't know how it works if you have a joint account), loans he was paying off, the electricity and gas supplier as the direct debit was from his account, house insurance, his employer and their HR dept, inheritance tax (there is apparently a complicated-sounding form despite the fact he had no money and owned almost nothing that wasn't jointly owned by me), land registry re the deeds for the house that are in both our names, the mortgage company, contact his GP/ dentist/ optician, the internet/ phone/ tv provider, the passport office, DVLA, work pension for death in service benefit, tv licence, water company, any other organisations he had a direct debit to which I will discover when I get access to his bank details, a lot of people/ companies/ places related to his various hobbies and the equipment for them
Much of this will irrelevant to you, things are complicated here because we had seperate bank accounts and most bills except the mortgage are paid by direct debit from his account and are set up in his name.
My list is long and appears overwhelming when you look at it as a long list, just pick one and make one phone call then make another when you next feel up to it, write down what they tell you (if they give you a new account number, if they need you to send a copy of the death certificate, etc) and tick off when it is done. It is definitely useful if you have another person who can make some of the calls for you and help you work out who should be on your list and who to prioritise if you can only face calling one person that day. Also, if anyone offers to look after your DC so you can contact people, mine are at school for several hours a day which gives me time to deal with some of this and meet with funeral directors and stare blankly into space in disbelief, I can't imagine how much harder it must be with a 2 year old.
Also, there is a service called tellusonce that will contact a lot of these people for you if you fill in one online form, I think (other posters please say if this is incorrect). I have been told about this, but haven't looked into it as his interim death certificates only came today.
Take care of yourself. The most important thing is to make sure you and DC drink, eat and sleep if you can.