Last week I did math flashcards with four kids, with four very different abilities, all at once. It was a great review for each of the kids on their own level, and was great fun to boot. I used multiplication flashcards, but it would work with addition flashcards as well.
Here's how it worked:
I showed the card to my 7 yo and he had to tell me what the two numbers added together equaled. Then I showed the card to my 9 yo and he had to tell me what the numbers multiplied equaled. Then my 12 year old, whose back had been to the flashcard the entire time, had to tell me what the two numbers were after having only heard their sum and their product. Finally my preschooler read off the two numbers.
Did you get that? Let me try again. Using the top card pictured at the right here, my 7 yo old would say, "5", my 9 yo would say "6", and my 12 yo would have to think what two numbers add up to 5 and multiple up to 6. She would answer "2 and 3" and then my preschooler would look at the cards, read off the numbers "3 and 2" and tell the 12 yo that she was right.
All four kids enjoyed the activity so much that they begged to do it more and were disappointed when I told them we would save it to do again next week.
Anyway, I got this idea for the book If I'm Diapering a Watermelon, Then Where'd I Leave the Baby?: Help for the Highly Distractible Mom by Carol Barnier, although I did modify it to include the preschooler as well. If you have never heard Carol Barnier speak, I highly recommend going out of your way to hear her. A few of her talks can be heard on her website, although it was the one with the same title as the above book and the one titled "Don't Miss the Gift in This Child" that touched me so deeply.