The term periodization specifically used for elite athletes who needs planning for long term say cricketer, soccer players etc. The children who don't have long term planning for participation may not require periodization. Rather encourage them to involve in routine playing to maintain physical health.

I agree with R. Khuman's answer. This term is maybe not apprpriate to use with children population. Involving children in different competitive sport could be ok, but it is different thanm specialization and periodization in specific sports. However, it easier said than done...

The Canadian Long Term Athlete Development (http://canadiansportforlife.ca/) program is a good reference that could serve as a basis, and recommends to specialize at the age of 15-16 years or more...

here's another interseting website: http://www.physicalliteracy.ca/play

Thank you for your cooperation

While talk about the children s fitness  concern,you can motivate them to play,as long as possible them with specific interval period. Dont recommend them to follow the periodization principle,because its meant for competitive purpose,those want to achieve the major competitions.