Unless you've gone past the point of just 'thinking' about buying, I suggest you study the timeshare opportunity on TUG for a few months before jumping in and regretting it later. You will probably never find a better opportunity to 'steal' a platinum Marriott timeshare and you don't have to rush into anything right now.
Buying a TS for trading only is one thing, but perhaps you should consider buying one where you'd be happy going 3 out of 4 years instead...and one that is in an area that you wouldn't get tired of once the kids have grown years down the road. There are so many timeshares in Orlando that resale prices are even more depressed that the deal you've found.
With kids it's important to remember that owning one that requires flights to/from each adds a tremendous cost to the annual overhead, compared to one you could drive to. The one you're looking at is not a 'lockoff' suite so that you could split into two parts for $75 and stay an extra week - or trade both parts of your split suite. Look at the annual maintenance charges too ... are they affordable now, and what will they be in 10 years with 5% annual increases?
Have you considered renting a timeshare each year instead of owning one? There are tremendous rental deals available on Ebay and on TUG classified that would give you a chance to experiment and learn from the experience ... at much less risk and commitment than owning. In many cases, you can rent a TS suite for less than the owners pay just in annual maintenance ... and to rent them, you don't even have to join Interval International.
Take your time ... study TUG for the next few months and then leap when and if you feel it's your time.
Just some food for thought...
Brian