I agree with you that the arrival day should not be too hectic. If someone has never been to WDW before and has been cramped in plane for a while, it might be useful just to ride around for a bit and get a lay of the land. From Epcot: take the Monorail to TTC, walk over to and around Polynesian (maybe have a tropical drink), take the monorail to MK, take a boat to and walk around Wilderness Lodge (time for another drink?), and then take bus back to Epcot, all of which will involve a fair amount of walking. 3 points: (a) Disney transportation does not usually go between hotels, unless they happen to be on the same route; (b) Disney buses may not run between the parks and Pleasure Island (you have to go a hotel or Downtown Disney); and (c) buses may not run from all hotels to all attractions if other transportation is available (e. g. boats at and walkway from Swan/Dolphin to Epcot).

One of the best suggestions I have seen for WDW (and have followed several times) involves realizing that the Epcot crowd is heavy in the front in the morning and in World Showcase in the afternoon/evening (slight different information than that provided in one of the above comments). Thus, on your first day, if you want to go to a park after checking in, consider doing most of the front of Epcot (you may need to delay the Fastpass rides). On a subsequent day, get there early, go to one of the Fastpass rides (such as Test Track) and get a Fastpass; then go stand in the regular line for another popular ride (maybe the new Mission to Mars). After you get done with those rides, World Showcase is probably opening but crowds may not have moved there yet.

I enjoy DisneyQuest but would not plan to hit it on the first day or two of a vacation if you're only going to do it once. Particularly in the summer, storms are frequent, and DQ is a perfect place to go if it will be raining (or particularly hot).