Bad Grammar in Children's Books

I feel terrible asking, but can a writer use bad grammar in a children's book?   They are just kids, right?  A child won't notice a slight rule violation.  Sure, they might struggle in school after reading my book.  I suppose they could flunk out of community college due to the language abuses witnessed at an early age.   I can't be held responsible if they one day write in their shop window:  "Theirs a bathroom around back.  Its green."   Shudder.

I don’t want to commit a heinous offense.  I merely want to write a preposition and then end the sentence.   Gasp!  

I want to write a sentence a child would say:   

There isn't anyone to play with.

I just can't bring myself to write:

There isn't anyone with whom to play.  (my character is not a snobby English lassie)

I have considered these escape routes:

He wanted to play with a friend.  (not quite right context)

He was tired of playing with himself.  (too obscene)

After weeks of worry, I stumbled on Grammar Girl's blog post Ending a Sentence With a Preposition.  She writes, "I know many of you were taught that you shouldn’t end a sentence with a preposition, but it’s a myth."   Now that's what I'm talking about!  I can finally cheer up.  Now I can write on.