Watch what comes back to the counter at the end of a family visit. The adults' cups are empty. The children's cups are half full, and they are going in the bin with the ice cream still in them.
You paid for that ice cream. The child did not want it, the parent feels vaguely guilty, and nobody enjoyed the last half of the transaction.
Smaller is not meaner
Four ounce paper ice cream cups are a small portion for kids' scoops, samples and mini sundaes. Serving a child at this size is not withholding anything, because the portion that came back half eaten was never going to be finished.
The version parents notice is different again. A cup sized for a child looks considered rather than leftover. An adult portion handed to a five-year-old looks like nobody thought about it, and the parent is the one deciding whether you get a return visit.
It lets you price the kids' menu properly
Without a smaller cup, a children's portion is just a normal portion at a discount, and the margin on it is worse than everything else you sell.
With one, the kids' item is a real item with its own size, its own price and its own cost. That is a menu line rather than a concession, and it stops the awkward negotiation at the counter about whether a small child needs a full scoop.
Make it obviously a kids' cup
The size runs in solid colors, polka dot prints and striped prints, all at the same case price, so choosing a bright print for children's service costs you nothing.
There is a practical reason beyond the obvious one. If the kids' cup is visually distinct from every other cup on the shelf, staff cannot pick up the wrong one during a rush, and a parent glancing at a tray knows immediately which order belongs to the child. That is the same argument for a color per size we made in choosing an 8 oz cup.
The cup does more than one job
Four ounces is also a mini sundae size, which is worth knowing if you want a smaller dessert on the menu for adults who do not want a full serving. The same cup, a different menu line, no additional stock.
It sits directly above the tasting size, so if you already run sampling as described in running a sampling station on 3 oz cups, these two sizes together cover samples, kids and small paid portions between them. Flat and dome lids exist at 4 oz as well, which makes pre-portioning for parties straightforward.
Ordering it
A thousand to a case, at the lower end of the range on price. Most shops underestimate how much of this size they will move once children have a portion designed for them, so if you are adding it for the first time, expect it to turn over faster than you planned.
The full set of sizes sits in the ice cream cup range.