I am so sorry for your loss. You and your children will be in my prayers.
I lost my husband to illness when I was 28 and my son was 5. In fact, it was the night before he started kindergarten.
Everyone handles everything differently and everyone's needs are different in this situation. However, I can at least tell you a little about my experience.
I cried and grieved with my son, but tried to find a balance for him. I did not want him to feel that his life was over too. In fact, he told me now that he felt uncomfortable spending time with his grandma (DH's mom) because all she did was cry.
I also put him in counseling as well as me. Since I am no expert in how children grieve, I wanted someone with some experience to guide me. Besides, I think I spent the first month kind of in an out of body like experience. I was wrapping up things like funeral planning, life insurance, and settling estate.
The first year was the roughest--the first Halloween, Thanksgiving, Christmas, birthdays, etc. It was hard to find joy when all I kept thinking was how he was missing our son open Xmas gifts, his first soccer game, etc. (To this day we still put up his stocking.

)
Now that he is older (it has been 6 years), he can pretty much let me know when he wants to talk about it. Every once in a while, he starts asking questions about him. Sometimes he just want to watch old home movies together. I will also bring him up occasionally if something triggers a memory. He loves to hear funny stories about his dad. I find so much joy in sharing those stories with him. I love seeing mannerisms he got from his dad, or the passion he has for his art that his dad had. I find comfort in knowing that his dad is with him, even if it is not physically with us anymore.
I will say that my son seems to get the most joy out of some of his dad's things. He brags about using his dad's tackle box and fishing rod. He keeps some of his dad's art projects on display in his room, from paintings to pottery pieces.
I make sure that he gets time with his dad's side of the family. It is hard because for grandma it has become her whole life and it is almost to the point of rubbing it in that he lost his dad. Thankfully, he is old enough that we can discuss how everyone handles something like that differently.
I don't want to say that it gets "easier." Somehow, the memories seem to transition from painful to joyful.
Please take care of yourself.