Last Minute Changes - Penalties?

[GotFids]

We are considering letting my son miss school so we can schedule our trip in May of 07. We will be using this as incentive for him to keep his grades up. If his grades are not where they should be, then he'd have to stay with Grandma. He's 16 and will be a Jr. in high school, so that is why we need to make this deal. He could not afford to miss a week of high school unless his grades are in good standing. He says he really doesn't mind staying at school, I think he is outgrowing vacations with us old people. But I'd really love to have him come...isn't the same without the whole family, you know? My question is...If he isn't able to go, can I cancel his ressie, are there penalties for doing so? Thanks for any suggestions.

Oh and just to clear up any confusion...my daughter is being schooled at home and making up work for her is no biggie.

Julie