It was very hard for us.
Doc's office gave as a couple of books and told us 'what to expect' from children in general. The books weren't helpful as they did not overlap with the age levels. My kids are 6th and 8th grades.
Not sure your situation but do not hold your breath (*** please note this was my case)
It was kinda our fault that we did not use the word "cancer". But we told them that i am very sick and will get sicker. But everything will be OK in the end.
My daughter, "mommy, i will help you", still laying on the couch.
my son, "are we done now?"
Basically, they are so involved in their lives. As long as their social lives are intact, they will try their best to ignore it.
What I learn much later from other moms....
a couple of things you can do
1) contact your school guidance counselor, tell her/him what you and your family are facing. she can confidentially send out a note to corresponding teachers, so they can give you heads-up or pay extra attention, as needed.
2) give them time to digest the news first, then, later, assure them that it is OK to tell close friends (or more!) to share their feelings.
3) talk to moms of their friends and share your concern. we totally break down when it comes to kids' stuff. if you are like me, my heart broke each time they have to give up their social gatherings. your moms will keep it together for you.
4) if your kids do some sports or activities outside of school, please do tell them too. they can arrange rides, or send you pictures when you cannot attend their showings, or classes.
5) leverage this time to educate kids. I have breast cancer, so I worries for my daughter. So we learn together about healthy eating and what to eat organic and what are safer, etc.
6) start doing some activity together. my daughter and I started to do "senbazuru" a thousand crane origami. To make a wish come true - once we are done, we will leave this to the infusion room, as inspiration art.
I have not found any common ground with my son - this is a hard one!
Good luck and keep us posted.