We just got back from BCV on 10/29 and DS just turned 5 months. We had a blast!! It was a much different vacation...slower paced, less commando, etc, but it worked.
We would go to the parks early in the morning (preferably the extra magic hours) and around lunch time (sometime around 12-2) when DS needed a real nap we would head back to BCV. Then I would nurse and put him down for a nap....then one of us would go out...either I would go shopping/exploring (love the outlets)...or DH would go golfing.
Then in the early evening we would go out to the Boardwalk, Epcot or DTD to walk around...although we were always back in the room by 8-9 pm. DS tends to "insist" on his bedtime, LOL! He gets pretty cranky by 8pm, so its our signal to turn in!
We had a great time. We took him on "little" rides...Small World, Jungle Cruise, the new Nemo ride, etc. He HATED the Mickey's PhilHarmagic....not that I thought he would watch it...but I forgot that when the champagne opened the corks popped air at him!
He also loved the pool! He loves kicking around in the water. It was really only hot enough one day for that....it really cooled off quite a bit while we were there and was in the 40's some mornings and high 60's/low 70's....while 70's is okay for me in a heated pool, I though it was cool for him.
Technically, you are not supposed to use sunscreen before 6 mos...my Pediatrician told me that it was because they dont want you to have baby out in hot sun! Well, with some common sense on keeping baby in the shade and covered (hats, sunglasses, etc) a little sunscreen is not a bad thing....just test it on him/her before you leave for vacation. We try to keep him out of the sun, but I worry about incidental sun exposure from reflections off pavement, water, etc. Talk to your pediatrician about what they recommend.
The baby care centers are awesome! The ones at Epcot, AK and MK are the best....MGM is a little small....but they were all great for a quiet place for nursing...by 5 mos they are curious of their surroundings and nursing in public may be too distracting for them.
PM me if you have any other tips as we pretty much took the trip you are planning! HA HA!
Oh, and he LOVED the characters! He giggled at Mickey and Chip & Dale and was IN LOVE with Mary Poppins! (He's a shameless flirt)...we even took him to the Playhouse Disney Breakfast at MGM and he loved JoJo and Goliath and the little Einsteins.
I have to say if it were our "one shot" at a WDW vacation I would not have taken him...but we are DVC members and we'll be back many times, so to us, it was well worth it! Plus I got my Disney fix in since I was took sick to go in Fall 05 when I was pregnant with him!