I have contracted to have a cinder block with stone accent, and flagstone top installed. The wall is to be 24" high.

The landscaper that I contracted with is using a sub on the wall. I over heard the sub telling the landscape company that he need more gravel and mortar for filling in the holes of the cinder block. The landscaper argued and told the contractor it was not needed...then...the landscaper knocked on our door and told us the situation..."if we want the block filled in... because we have kids... it will cost 250 dollars more."

Any way... who is correct... should the block be filled in? Thanks! JCR

I don't see what having kids has anything do with filling in the block.
What's their reasoning? They afraid it may fall over? Is this wall decorative or is it holding back earth?

It appears the mason wants to make this wall "sound" and doesn't want any future problems with the wall and filling in the cavities will definitely help.
The landscaper, if he buys more material, looses some of his profit because he didn't relaize what all the mason needed to build this wall.
So now it comes down to loose money of make up an exuse to cover his potential loses.