Okay - after taking everyone's comments into consideration, this is what we'll do next week:
You'll get a point for every mile you propel yourself (run, walk, elliptical) with a max of 13 earnable points. You can do it all in one day if you like, or you can split it among the 6 days. Whatever. So instead of that weekly challenge being worth 7 points, it will be worth 13. I think we definitely DO need to put a cap on it, or else I literally might kill myself trying to run 100s of miles. : ) And if I'm dead, there won't be anyone to send you your winning check!
Every other weekly challenge we've done has been in ADDITION to the "Exercise 30 minutes" point. So, as much as I dread how much TIME this will take, we should keep it the same. Otherwise you'd be getting double points for running/walking each day. If you've truly been exercising for at least half an hour each day, for six days straight, for 11 weeks, pushing it up to an hour shouldn't be difficult - your body can handle it. There have been lots and LOTS of days when I exercise twice anyway, and I'm sure I haven't been the only one.
Plus, this will be a good, strong finish to our entire fitness challenge! So say you run for an hour - the first 30 minutes will count toward your "exercise" point, then the rest of the mileage will count toward your "marathon" miles point. Get it? I'm planning to break it up a lot and do, say, 30 minutes of a DVD workout, then run for 3 miles each day.