Well even as much as I love Fort Wilderness the whole tent camping option - or heck any camping unless we are talking a luxury 5th wheel type motorhome - does not appeal to me. I need a nice little Fort Wilderness cabin with a shower, air conditioning, cable tv, a comfy couch, ect. I am obviously not one for roughing it
Plus I always feel so sorry for all of the tent campers on the days when it downpours
It just seems like everything in their tents would be damp for days.
So if I only had those 2 options I would go for the Dolphin in a heartbeat. I have been in the Dolphin once and it seemed very nice to me and the location is really great too. However, it didn't feel very "Disney" to me so I wouldn't really ever want to stay there. But if I had a special rate like you do I might would maybe "sacrifice"
and stay there afterall. I have noticed from some of your other posts that you have stayed at the Dolphin before and I am assuming that you liked it since you are considering staying there again. I would stay at the Dolphin but take a day to visit Fort Wilderness and explore, do the petting zoo, hay ride, campfire sing a long, ect. You could even check out the tent camping areas in detail so you can see if you would maybe like to do it on the next time you go to WDW