This is what three toddlers can do for or rather to a house, more specifically my toddlers in my house.
These are just two of the rooms that had toys scattered through them the other day, after a fun day of playing. What you need to remember is that toddlers can also help undo this. My children know that picking up their toys is something that needs to be done, not something that magically happens or is mom or dad's job. They help pick up their toys before nap time and bed time. (Yes there were this many toys brought out between nap time and bedtime.) The lesson is that even young children can help. It's much easier to start with good habits than to try and correct bad habits, not that my children don't have any of those (my sons are napping on the couches at the moment instead of in their beds). Even my 1 year old is catching on. Some days he helps without prompting, other days I may hand him a magnet or two and ask him to please put them on the frig. The point is that he's already learning that it's his responsibility along with all of the rest of us.