Jack,
The veneers will be oriented with the grain horizontal, but having said that, your proposed approach of slip veneering across each row of drawers, whether it be a double drawer row or a triple drawer row, would be less disruptive to the eye that the threes slipped and the twos bookmatched, which I am afraid would look jangled.
The other solution I was considering might be to book match the doubles, and on rows having three to book match the outboard drawers to each other, and split the center drawer front veneer into two bookmatched halves, which were each a slip match of their outboard adjacent drawer.
I like your solution; thank you very much for your help.
Karl