I read there was a way to get more than one child to pick the same mushroom. If you don't want to know, don't highlight the following text. Pause your game <space bar>, then pick up your kiddos one by one and drop them on or very near the mushroom (you will see the status message "picking a mushroom", then unpause your game <spacebar>, and away they go. I have seen up to 4 or 5 kids get the same 'shroom and you get food points for each.
Sometimes they jam up around the food bin and I think not all the mushrooms get counted. But you're good for more than one, in any case.