If you are worried about the distance... Wdw theme parks aren't really for you. Can't walk a quarter mile? You aren't going to last and need a scooter.
If you are worried about the environment a simple solution would be to make the path a wooded one so it would be shaded and in theme.
The suggestion of moving walkways just sets the wrong expectation.
That's a bit much. I'm talking about one park and one particular distance.....not walking in general. Suffice it to say, you walk a great deal in any of the parks. But after hours of walking and deciding to head off somewhere else, or just go back to the resort, it does seem a very long walk back to the buses at Animal Kingdom as opposed to the other parks.