My DH died unexpectedly overseas at 31, and we were also one of those couples who did everything together, laughed together and were at the beginning of a fabulous life. We had plans and dreams and then suddenly, it was all gone. He died of a heart attack 5 years to the day that we met.
In the immediate afterwards, I used to look in the mirror and wonder who that person was. I didn't recognise her. And I felt as though I had lost a limb. I had definitely lost my dreams.
You've had a lot of useful advice already, so I'm not sure how much more I can add. But I will say that of the people offering to help and not being specific ("let me know if there's anything I can do" etc which used to drive me nuts), tell them what to do. Just tell them. It's going to help you (have the kids for a day etc), and it'll help them as well, particularly if they were close to your DH and they are grieving too.
It's too soon yet to go to grief counselling. You're still in shock. In the beginning, I used to wear mascara when I had something important to do and didn't want to descend into a crying spell (seeing the bank, or the solicitor). I would tell myself "I can't cry just yet, or my mascara will run". Silly, I know, but it worked. Little steps, each day, to get through it.
One other thing - if your DH died overseas (assuming he was British) have you reported the death to the British Embassy there? They will register the death and you will (I think I'm right on this) have a British death certificate. If not British, then maybe the Embassy from his country of nationality?
Give it a couple of months, and then find a grief counsellor. I did - she saved my life. She helped me come to terms with it, and deal with my grief properly. This time is awful, and I'm so sorry you're going through it. xxx