Not necessarily.
We are booking buffet restaurants with ours, so that everyone in our party can pretty much just eat what they want. An example of the price saving on this is, the full cost of the buffet dinner at Cape Cod in the Newport Bay Club hotel for one adult, one child, is 40 euros (ie around £33). I've paid in advance with my half board plus vouchers, and they are accepted as payment in full at the Cape Cod. That meal has only cost me £25, as its prepaid. You also get a soft drink including with the half board vouchers, and you don't always get that included in the buffet prices when you "pay on the day".
But, for example, you can order from the normal menu at Cafe Mickey, and then when you come to pay the bill, they will deduct the face value of the half board vouchers you give them. Half board plus adult vouchers have a face value of 25 euros each. I'm not sure how much childrens half board plus vouchers are face value - is it around 11 euros?