If a loan for more than $25,000 is secured by a Time Share, and the interest in the Time Share is perfected with a recorded Deed of Trust, would that Time Share be considered "Real Estate" or a "Dwelling" for purposes of triggering disclosures under Reg Z?

It's a partial interest in real property - I would have to say yes. I hope that you got an actual appraisal and didn't go by the sales price. Most of these time shares are pretty much worthless on the secondary market after the original purchase unless you are talking about a primo spot.