Well, let me see if I can answer a few of those questions..
We didn't take any of the tours, walk to FW, or eat at Artist Point. My 3 and 6 year olds would have balked at those things. Though we did go over to FW, as my brother-in-law's family was camping there.
The transportation was great. We only had one really bad experience with an Epcot bus one morning. The bus was the first Epcot bus in over 35 minutes, so we filled it up. The driver was clueless, as he headed over to FW anyway. He couldn't get the automatic gate to open at the campground, so we spent 5 minutes backing up and going forward, over and over. He got out of the bus, got the gate to open, ran to the bus, but the gate was already down! We did finally make it to Epcot at about 9:30 am (we were at the bus stop at about 8:15).
Finally, the weather. I personally don't think it was bad at all. About the same as I'm used to in Houston. Our 3 yo and 6 yo kids both walked everywhere (no stroller in any park) with absolutely no complaints. There were a couple of days I know we walked 4-5 miles! The only places that the heat seems a bit worse is AK (the jungle foliage blocks most of the breeze) and the area around Splash and Big Thunder at MK. For some reason that area seems hotter than the rest of the park. (more humans and concrete I guess) Drink lots of water and have fun, it's not all that hot.