I was diagnosed the day before you. I have 3 girls older than your kids, mine are 11, 13 and 19. The 19 knew from the outset but the younger 2 we had to tell. I have been completely honest with them.
They initially were shattered but we all had a good cry and hug together. There is no good way to deal with this but you can't be strong for them 24/7. If they see you trying to be strong they may think they need to be strong as well. They need to know that it's ok to be scared, sad, angry and that all of these emotions are normal. If you allow your feelings to show, it also gives them an opportunity to comfort you. That in itself is good for them. The cancer council has an excellent booklet on talking to kids about cancer and gives guidelines for each age group. It's free and you can either order it online or your local treatment centre might have one.
Good luck sweetheart and know that we are all here for you on your journey.
Big hugs xxx
Dan