You may find this odd, coming from a male to respons to, but since I've been there done that, I'll offer you this. As a true believer that everything happens for a reason, our response back in the day was that 'God felt it wasn't time yet for the baby to arrive'. Although it's heartbreaking and a difficult time for the adults, the little ones (under 10) as you've stated, will share the pain but with your guidance will also be able to cope with it.
When we went through this experience, we had many unanswered questions that ran through our heads and it was hard, but we we're determined to believe that it wasn't the right time however God would let us know when it was.
You may have a few more questions asked by your young ones but stick with that belief and before you know it, if you desire, when it is meant to be, it will be.
You can do it!!!!!!!!!!!!
I hope I provided a little bit of insight. I only responded to this question because I truly mean what I've said and 16 and 9 years later after two healthy kids, although we've never forgotten that day, the conversation is rarely, if ever brought up.