Not to pile on but I am also confident that such an item is not deductible. There was a FAQ on the IRS site a few years ago specifically on this subject with a negative conclusion, they later substituted the vacation home FAQ. Dave McClintock is a retired CPA and Timeshare expert, you can find his advice on this subject
Here. Many have done so and not been audited but it is an invitation to an audit IMO as well as an automatic exclusion on that audit. However, you can rent the week out, donate the proceeds and take a deduction on that amount if you want.