Will I need a Phonetic Farm for each of my children?

You can use one for all or get one each. The Phonetic Farm folder is wonderful for reinforcement. My 6 yo loves to pull it out and look at it. If you have more than one child, they will enjoy having their own. Just beware that the stickers are permanent, so be sure they put them in the right place the first time! I keep all the stickers in my notebook.