I registered for Book-It last year at some point, and am trying to decide now whether or not to actually participate. It doesn't help that I've been reading Alfie Kohn over the last few weeks.

(I went ahead and registered because I hadn't made a decision at that point; apparently I have yet to come to a decision,

.)
My kids are already heavy readers, and one of the things I like about BI is that you can set your own goals. I discussed with my oldest (7) what sort of goals we would like to set for her reading, and if we would even want to set goals. We talked about setting a nonfiction-reading goal, since her favorite books to read are, of course, fiction. We did NOT discuss the idea of rewarding her for those goals with pizza.
(Kohn, of course, frequently cites data on how rewards and "bribes" reduce the intrinsic joy of whatever you are rewarding; in this case, how a child who reads to get pizza begins reading to knock books off the checklist rather than the joy that comes from reading/exploring.)
On the one hand, there is the homeschooling mom who wants her kids to love reading and do so for its own purpose - which they do now.
On the other hand, there is the frugal, SAHM of four kids on a tight budget who would love to go out for pizza and get a portion of it for free.
Is it possible to have my kids set the goals to work for, achieve them, and then go out for pizza without particularly linking the two of them? (and does that take away from the basic nature of the Book-It program?) Am I deluding myself about this?
If I am understanding Kohn correctly, it is not so much the setting of goals that destroys the intrinsic rewards but the act of the external rewards. Is it possible, then, to walk the line? Or should I just give it up and go out for pizza once a month for the heck of it?
Any thoughts would be appreciated! Thanks!