Preschool Blocks

EMan is working his way through the Math-U-See Primer book.  He's gotten bored with the reviews happening in preschool and was ready to move on.  We flew through the first lesson and then stopped short at his instructional level.  He is working on identifying combinations that make ten.  I knew I needed to pull out CJ's old set of blocks and just play with them making groups of ten.  So, this is what I've done with what's on hand.  I happen to have a ton of unifix cubes.  I picked some colors that matched Math-U-See the best I could, stacked them together and then labeled them with numbers.  It was then Eman's job to identify what two stacks of blocks would equal 10.  Though successful, I would love for him to work more on this concept, however he is bored with it already.  Any ideas to make the game more fun?