The final tally:
Chocolate bars: 28
Potatoes: 13

That was lots of fun. (Especially for the parents on the sidewalk shouting "Potato!" when they heard me describe the options, and the two teenage girls who said "Oooh, now we can make poutine!" - and it would have been closer if one young lad had not been forced by his mom to put back the two potatoes he chose.)