Broccoli at school

We've had a sort of deal with Chloe for a while now.  She knows that we would really like her to eat her vegetables at school.  Sometimes she does, sometimes she doesn't.  On the days that she doesn't eat them, she has them for dinner- or her after school snack.  This makes a lot of sense to her, and helps us prevent waste. 
We do try and put things in her lunch that she enjoys, not expecting her to really go out of her comfort zone at school.  So, we frequently ask her about her preferences, and she tells us if she thinks of something. 
Recently, she had some broccoli and carrots in her lunch.  She hadn't eaten them at school, so she was having them for dinner.  She asked if broccoli could not be one of the vegetables she got at school. No problem, she eats a fair amount of broccoli at home. 
The next day she was sitting in the counter and said to me- "Mom, I have an idea- How about you put broccoli in my lunch and each time I eat it, I can get two marbles.  That way you can teach me to eat my vegetables at school." 
I was so tickled at her saying this, the idea of her helping with ways to teach her how to be healthy.  I laughed out loud.  I didn't mean to, but I'd embarrased her.  When this sort of thing happens, she feels like I'm laughing at her.  I always feel so terrible.  I try to tell her I just love the way she thinks, and the things she says make me so happy I laugh sometimes.  Still, it doesn't feel good to her.  I try not to have "big" reactions to her precocious moments... but sometimes I just can't help myself. 
I think its a great idea, actually.  But I'm not sure if it is really teaching the "lesson" if she already knows the purpose.... but at any rate, it was her figuring out ways to make good choices and get more marbles.  And that's pretty good to me. 

I gave her carrots and broccoli in her lunch the next day.  She ate the broccoli and not the carrots.  And asked for her marbles.  I'm not sure why I think it's a little silly.... I guess there's no harm done.