Ice cream can be obtained by two ways (not counting the one the kid is blocking). There's a store outside the Grand Hall on sunny days, and there is one in a hidden room in Spinel Town (it's opposite the museum rooftop entrance). The one in Spinel I believe is cheaper, plus if you buy a Vanilla icecream from the Spinel vendor, you will get a pleasant surprise...
As for the kid himself, he's in the candy shop (left of Obsidia Park).
But yeah, no idea what the choc or berry one does. Healing? More friendship?