This whole discussion is so interesting from a food perspective. Here are some more thoughts:
1. What constitutes a healthy snack? Fruit by its nature, is sugar laden, so tons of fruit, is also not good. Nuts can be salty, juice is full of sugar, etc...
2. Kids are picky because parents have made them picky (excepting special needs children). If kids have been fed chicken nuggets and pop, then that is what they are most likely going to want to eat. All of the new research is showing that this generation of hugely picky kids has been made picky by: chemicals in foods (only crave salts/sugars/fats) and parents who don't model or provide good eating for their kids. Kids can only eat what is in the cupboard, as last time I checked, 4 year olds can't go grocery shopping on their own. LOL! So, once again, we have the home world, crashing into the school world. What's the best way to deal with this? Classroom contracts perhaps are not the best way.
3. School lunches are horribly fattening - my parents are restauranteurs who used to run several highschool cafeterias, plus, I'm a highschool teacher, so I can assure you that school lunches are horribly full of chemicals and fats. Yuck! We joke that you can set a foundation on your house with that nasty gravy! Teens love this kind of food, it's cheap, and commercial food products are made this way, as most of it is packaged/processed in some form. My family actually made homemade food, but after awhile, it got too expensive, and our board couldn't afford it any longer.
4. Kids don't need birthday treats at school - we never had this when I was growing up, and it was just fine. There are lots of other fun ways to celebrate birthdays without always having to involve food.

Donating a book to school is a fabulous idea - I've been doing it for years. A book is going to serve much more good than cupcakes and pop. Your child can eat the cupcakes and pop at his/her birthday party at home.
Such an interesting discussion, Tiger