Having small, age appropriate responsibility is good for children. It increases their self esteem and makes them feel more involved in the family. Tidying up toys once they have finished playing with them is a good place to start. Some children will cooperate with this task without a problem but if your kids are like mine they will hate tidying up!
Try turning it into a game. Children are much more likely to engage if it is fun and if you are doing it with them. Have a race! Who can pick up the most toys and put them into correct boxes? Most children are competitive and will want to win.