OMG, my kid was the one who used to bite the daycare kids! She is reacting to him not sharing toys and being a toddler
I agree with Apples and Bananas- you aren't going to win with this one. Just let them know that your working on it with Timmy. You mentioned above that you are working on sharing with him so it's the truth. At this point they are only worried about their own. Try not to take it personal. Then end the email off with, 'The Toddler Creed' to lighten the email
The Toddlers Creed
If I want it,
IT'S MINE!
If I give it to you and change my mind later,
IT'S MINE!
If I can take it away from you,
IT'S MINE!
If it's mine it will never belong to anybody else,
No matter what.
If we are building something together,
All the pieces are mine!
If it looks just like mine,
IT'S MINE!
If it breaks or needs putting away,
IT'S YOURS!