When we went for our honeymoon, we generally did one park per day (6 days... 4 parks plus Downtown... we're not water-park people

).
This time around (3 weeks ago), we took a different approach that really worked well for us.
First of all, I should mention we were staying on-site, so we had the Extra Magic Hours available to us... we didn't take advantage of the morning ones (we didn't really see the point, since they're pretty much a 'free for all'), but in the evenings one park per day is open for about 3 hours past regular park closing... in some cases, that means until 2 a.m.!! ; It's only for folks staying on-site... 2 hours prior to regular park closing, you can get a wristband... and once the park closes, they start checking wristbands to get onto the rides (not all rides are open after-hours... and it's good to know in advance that the food concessions generally close at the regular time, so don't expect to be able to get anything to eat).
With the Park Hopper passes we generally structured our days so that we spent a few hours in the morning at one park... then went back to the hotel (or Disney Quest one day... we had the Plus option on our passes) for the middle of the day (when we were there, the daytime highs were in the 30-35 Celcius range... just a little bit toasty... and since some places like MGM, Dinoland U.S.A., ; and parts of the World Showcase at Epcot are black-top paths, avoiding them in the full heat and sunshine was nice)... then went to another park from 3 or 4 until we got tired or it closed... or until closer to wristband distribution if we knew we were going to do the night-time Extra Magic Hours. ; (For example, one day we did 1/2 of Epcot, went back to the hotel to cool-off, then went to MGM for Fantasmic and Extra Magic Hours)
It worked well for us... we avoided the worst heat and crowds and didn't stay in any of the parks long enough to get bored or tired, but knew we could go back again later in the week.
Also... when we were there, we heard that Animal Kingdom was going to be open 'til 8:00 'til Fall due to the expected increase in attendance because of Expedition Everest (so worth the line-up, in our opinion... we rode it a few days before the official opening). ; If that's the case, though, I wouldn't expect animal viewing to be available past about 5 p.m.. though, at least for the Kilimanjaro Safari... the animals have a routine that includes moving them to barns at night, and some of them don't take well to variations in the routine.