If you are really quick, 3-4 kids can be placed on a mushroom even when the game isn't paused, but that takes practice, patients and shouldn't be done when there is a desperate need for food, since it can cause the kid who already picked one to drop it.

To know when to stop placing kids (in pause mode): I watch the status as I place each kid on the mushroom, once a kid is put down and it doesn't say "picking a mushroom" that is the end and I unpause the game and hope that they all make it to the food bin.

I have a few favorite spots to find mushrooms. One of the best is up near the cactus. I can "focus" the window where it is likely for three different spots and keep an eye on new mushrooms.

But try running in 1/2 speed. They will eat less often and you'll be able to get more researching done!