I'd suggest DL, as well.
A large portion of Fall is still hurricane season at WDW. At DL, your weather will likely be very clear, no rain, relatively low humidity (especially compared to WDW)....meaning, physically you all will likely be a LOT more comfortable at DL.
I know they've been giving the free dining plan at that time of year, but considering you only have yourselves and one itty bitty kid who isn't going to eat much, I wouldn't consider the dining plan a deciding factor.
DL is awesome with little ones....it's easy to park hop (it literally takes about 90 seconds to walk from DL to DCA - check it out on Google Earth), everything is close together, and again...you won't have to really prepare for things like multiple daily downpours (which personally, would be enough on its own to completely deter me!).
Another consideration is that you might be able to do DL cheaper, because it's really easy to do all that you want to do in just a few days time. As previous posters here have said, WDW can take up to 2 weeks and STILL leave people feeling like they didn't "do it all".
I did a TON of reading on the boards and other places, because we have 4 kids and have considered trips to WDW. Every time I read about people having to wait for busses, then get onto crowded busses with tons of sweaty people, and spend all day in the muggy ickiness of florida (so much so that they often mention going back to the room just to change out of sweat soaked clothes and into dry clothes), I just go right back to planning the next DL visit, lol.