Yes! My son asked me the other day where do babies come from I told him what I think is an age appropriate response. Some things kids are just not able to understand. And we as adults should not force them to understand adult situations.
Yes, no matter how old they are, when you find out just before Christmas that the doctor says there is nothing they can do for you anymore, but they will keep you out of pain until the end! By Not telling them how bad it is until after the holiday. Selfish to have one last Merry Christmas, no it might be the last good time they have with you! Tell them the week after!