We just got back from our first family trip with me, DH (with a bad back), DS10 and DS12. Here's what we learned:
While I had everything planned to "perfection" so we could see it all, it was very apparant after the first day that plan was NOT going to happen! I did not count on everyone running out of steam so fast each day. DH was in a
ECV most days, which slowed us down considerably. I had figured the boys would not need "break time" in the middle of the day to go back to the room and rest...WRONG!!!
I learned that the "weakest link" theory is right on the money. Your family "chain" is only as strong as the weakest link. When someone has hit the wall, give it up and do what is necessary to get the chain strong again. Most days, that was going back to the room for a rest. We ended up cancelling 2 dinner ADR's due to this, but it was okay...we weren't that hungry and ended up saving some money!
I agree with the OP who said that avoiding lines was what helped improve the kids' behavior...we used FP's whenever possible, as well as morning EMH a couple of times. Never waited more than 20 min. for anything.
Letting the kids know that this was not "all about them" and that we would all make compromises for the enjoyment of the family as a whole was key in getting the best behavior out of them.
The other thing I learned? Not to deny my kids something just "because". Our first park was AK and my DS10 wanted to mix a bag of jelly beans from the first gift shop we were in. I told him no, thinking that was not a good choice for lunch (!) and he shouldn't spend his $$$ on the first thing he wanted. I told him maybe later after lunch and there would be lots of stores with the same thing. Well, he moped all day and kept asking when he could get the jelly beans. He is not a "Gimmie" kind of kid and all he asked for all day was these stupid jelly beans! By the time I said okay, we couldn't find any other shop that sold them and couldn't find the original store either!!! Sooo...I learned a lesson and we got the jellybeans the next day at Epcot as soon as we saw them. He did not ask for one single thing the rest of the trip!
I also agree you shouldn't force kids to ride things they are scared of...however, my kids did say lot's of times, "I don't want to go on that...it looks stupid!" We told them, too bad, WE want to ride it. 9 times out of 10 they would say "That was GREAT!" So, sometimes, you should make them do something they don't want to (as long as it is not due to true fear).
Overall, I think let kids know what you expect and they will live up to your expectations.