One more thing- those 7 days (if it is 7) are calendar- not business- days. So before you wait until Monday, make sure today isn't the last day. If it is, try to find a post office that is open today for postmarking (I know there are some in many communities nationwide). If not, at least fax a letter today and follow-up tomorrow with a certified letter acknowledging your fax.
As I am sure you've already surmised, there are some very different opinions here about whether you should buy directly or resale. You can easily access those threads by doing a forum search. A month or so ago there was a rather vehement and lengthy thread, and it would be good for you to take the time to read through it to make the right decision for YOU.
The bottom line is ...well, what usually is the bottom line: $$'s. You save money- a lot- by buying resale. You give up the up front incentive points and the ability to trade your unit for points; everything else is the same. Different people have their own ways of evaluating the value of those incentive points (largely, it depends on how much value you place on getting business class flights and whether you want to evaluate hotels at rack room rates or whether you travel overseas and either do it a bit more modestly or find great hotel rates elsewhere). The same methods of evaluation apply for whether or not trading for points makes financial sense. But let's not repeat the earlier threads here. I will just add, in the sense of fairness, that those who advocate buying direct feel that they get more than their money's worth from the points while others feel that they can buy points from Marriott if they want them without any financial outlay.
An issue here may be whether Enclave resales are available and, if not, is owning an Enclaves unit worth $20,000 more to you than a regular Shadow Ridge resort unit?
The bottom line is that you have not given yourselves the time to really understand things and evaluate what is right for you. As Eric said, the opportunity to buy will be there tomorrow (or next week/next month) but you only have a limited opportunity to rescind. You may very well turn around next week and agree with Heidi that buying direct is the best way to go for you. But, I'd hate for you to read more on this Board over the next few weeks and then kick yourself. While I was initially almost going to buy direct, the more I read the more I realized that would be a mistake and I would have regretted it; the same may or may not apply to you. You may really love the Enclaves and be willing- and able- to afford the price difference. On the other hand, money may be dearer to you and the 20K may be worth a little work and possibly even buying in the original section. That's a personal choice. But it is nice to understand the options.
Whatever you decide, good luck- and welcome to Tug!!