Just so as you know, walking from Swan+Dolphin through EPCOT to the monorail station is about 1.3 miles and is like walking From the Main gate at Magic Kingdom, down Main street to the round about in front of the Castle, left through Adventure land, back up through Frontier land, through Fantasy Land behind the Castle, over to Future World, back to the round about in front of the Castle and back down Main Street to the main gate.
The buses are not that bad and will get you around much quicker. Don't be afraid of them. Try to time your bus trips in off times. Don't take them first thing in the morning, but a hour or so after the parks open isn't bad. Same thing at night, DON'T take the bus after the fireworks show, but an hour later is ok.
WDW is huge! everything at Disneyland Cal could be dropped into the Magic Kingdom and it wouldn't mess with the lake and 3 hotels that are in front of it. Your going to be doing a lot more walking than you think, and saving your feet a few steps by taking a bus will be a blessing by the end of your week.