A penny a point is reasonable value - I get a little more than that actually, but if I did not have a large stash of points I'd probably take the cash. Marriott points are at their most valuable when you reach the 270k-330k level.

More importantly, whenever I've done timeshare tours in the past, they've offered up a lot more than $100. I've done one for 20,000 points and one for $225 in resort credit. I also did a third one where the rate for my villa was essentially the "reward" (I valued what I got in that case at about $400, given what I would have otherwise booked). I believe Marriott restricts you to one tour every 18 months. I also have noticed that they no longer aggressively market to me - I used to get slick direct mail pieces frequently for Hawaii, Florida, Arizona, and elsewhere. I suspect that my three-time non-buying status is definitely recorded in their systems.

If you haven't toured already and are there for a week, I might sniff around for a better presentation offer... If your particular location is nearly sold out and they don't need to sell many units, they might say "take it or leave it - we have other buyers". But considering that the timeshare market is somewhat soft right now, they might be a bit more eager than $100 to do a presentation.

EDIT...based on MacDaddie's post...I definitely agree that if you accept any kind of gift certificate you should definitely validate that it is truly cashlike. Either a gift card or a gift cheque that can be handed to any Marriott clerk, anywhere, to settle any kind of hotel charge.

In other words, you're at your parents' timeshare property for a week. I'd want to turn in my gift cheques to settle my weeklong food/bar tab on that stay.