Hi There,
We were at WDW last month; it was my kids' first trip there (and I hadn't been there for many, many years).
In response to some of your thoughts:
As I live one mile from the Milwaukee County Zoo, we're there a LOT (we have an annual membership). Animal Kingdom was my dd8's favorite park. It's nothing like the zoo; Kali Rapids is great, the safari was fabulous, and the Nemo musical and Lion King shows were top rate. My kids both loved Expedition Everest. The park is a much different feel than the other WDW parks; more laid back and relaxed, IMO. The cast members are amazingly knowledgeable and friendly; take the time to chat with them!
If I were going to skip a park, it would be Hollywood Studios. There are more shows there than rides, and it was the least favorite park of both of my kids (they liked it, just not as much as the other three parks). Alternatively, I would keep the park hopper and do the front part of Epcot (Soarin', Mission to Mars, Test Track) and then hop to Hollywood Studios. My kids weren't all that interested in World Showcase, and were done with it before we were halfway around the lagoon. That's my family though; maybe your kids are different.
Try to see Hoop De Doo Review for your sit down if you can. The food isn't bad, and the show is a lot of fun!

My kids LOVED it; it's what they're telling people about over and over. Yes, it's expensive, but remember it includes tax, tip, all you can drink soda/milk/beer/sangria AND a fun show!! Call NOW to book it (or any other reservation); don't count on being able to walk in for any TS restaurant. It's very, very popular, so it may not be available; I'd call daily and try for ADR's, because people do cancel sometimes.
I don't know what time your flight leaves Chicago. Our flight left Milwaukee at 8am (direct flight); we landed at Orlando about 11:30am their time. By the time we got to MK it was 3pm. It takes time to make the transitions from airport to hotel to parks.
We didn't do the dining plan either, and were very happy with CS/snacks (be sure to try the Dole Whip and turkey legs!).

Don't count on the lines for rides/attractions decreasing during mealtimes; I didn't notice that happening at all. The only time the lines seemed thin a bit was when people were settling into their spots for parades or fireworks. I remember reading somewhere about someone who enjoys watching Illuminations from a hammock at CBR; I think that sounds wonderful!!!
I used the Unofficial Guide for planning. Yes, it's a ton of information, but IMO it gives you a lot of sound advice. We tore out the touring plan for the park we were hitting on a particular day and used that as a guide, but tried to stay somewhat flexible too. We skipped the parks that had EMH, as those are the most crowded parks of the day (and you're going at a very crowded time to begin with). The Unofficial Guide also has you avoiding parks with EMH.
I'd drop the park hopper; we didn't hop because we felt the time involved going from one park to another was a waste of our magic time, and we were very happy staying put in one park each day.
If you have any other questions, let me know (feel free to PM me).
Have a fabulous time!
Anne