I wouldn't recommend either at all IMO. The Grand Caravan is a notorious for being a rental fleet special and the seats are unsupportive with my 5 experiences renting this van. Very tinny fealing and the interior is cheap.
The Ford Edge, although better, probably doesn't have much more life in it and the seats are unsupportive. The Mazda CX-9 has the same Ford platform, but drives better in every way and is reliable.
If you care about seat comfort, look at a 2008 Mazda CX-9 or 2008 Toyota Highlander.
The CX-9 is based on the Ford Edge platform, but is more reliable (get one 2008 or after because that is when they used a Mazda engine, not Ford), it is quieter than the Edge, and it is much more fun to drive than the Edge. As with most Mazdas, the seats fit thinner people better than wider people, but are very supportive and comfortable on long trips. It's avaiable in AWD. I found many 2008s near me top of the line for $15k.
The Toyota Highlander is another good choice. It is more comfortable than the Mazda CX-9 in terms of ride and seats, but is not fun to drive and is a little boring. If you put a lot of miles on your car (I'm assuming you do), this should be at the top of your list. It's very reliable and will last you past 200k miles, something the Ford won't do. It is a great highway cruiser and get better gas mileage than all the other cars I've talked about.