Lorix,
The Grotto Pool with the slide is closer to the Dolphin, but we stayed with DD's 7 and 12 at the Swan last year and the walk is not that far. If you look at the photo of the Swan that normally appears at the top left corner of the web page, that photo was probably taken very close to the Grotto Pool looking back at the Swan, and it's not as far as it looks in the photo. There is another rectangular pool directly adjacent to the Swan that I would guess is usually pretty quiet, but you would want to walk to the Grotto Pool without a doubt. On the way to the pool you pass a sandy beach on the lake and some playground equip. We loved the Swan and are staying there again. We're coming into Disney the day you are leaving as a matter of fact and got the same rate for later that week.
As far as the walk to the Boardwalk, the Swan is a little closer, but the diffrence is minor. There is a walkway that crosses the lake that connects the Swan and Dolphin, and the Swan is on the end of the connecting walkway closest to the Boardwalk.
All in all, I probably wouldn't base my decision on the distance to the pool or Boardwalk, but on which hotel looks more appealing to you. We stayed at the Swan last year because the refurbishments at the Dolphin had not been completed yet (I assume they have since been completed for some time now). Since we were completely satisfied with the Swan, we decided we would stay there again instead of trying the Dolphin. The Swan lobby is not as large or grande as the Dolphin, but is beautiful nonetheless. I do agree with a previous post that the Dolphin has the advantage of the 24-hour Tubbi's cafe. But again, that would only be a short walk across the lake to get there from the Swan.
There are some nice aerial shots you can find on the web for the Swan and Dolphin that will give you a better perspective of their relation in distance to the pools and Boardwalk.
Here is a link to an aerial photo of the Swan and Dolphin, note that the grotto pool is just cut out of the picture at the bottom left corner and the Boardwalk is just above the Swan on the right side of the photo.
http://www.disneypix.com/2000ft/Roll2/Roll02_018.htm