I am not a veteran, but your questions spoke to me. I am planning a trip now for my family (11, 8, and 3). We have done a 2-week road trip up Hwy 1 in CA, Bogota and Cartagena Colombia, and Italy for a month, yet going to DW seems like so much work. We did go to DW 4 years ago when there were just 2 kids.
Here's what I have learned from my previous DW trip and other travels:
1) Identify your goal for this trip!
My goal is for my family to have fun together.
For some it is to ride every ride, or to meet certain characters. Having a goal will help you to organize and prioritize. Choose one goal, because more than one means that you are then organizing and prioritizing goals, and that's just too much work for vacation.
2) Streamline!
As a fellow mom of three, I know that you know how to do this with expert precision! But, you also know that moving a family of 5 is like herding cats. Apply this knowledge to DW x 5!
DW is intense with so much to do and see, so take as much intensity out as possible by making things really easy for yourself.
For me, I can't have an elaborate schedule with a particular order and times for rides. One child will need to go potty, and as soon as I walk out of the restroom, then another will want to go potty, and the whole plan will be off. When we went to DW the first time, I had no plan whatsoever. We walked into the park and went on rides as we encountered them (to be fair, it was mid-Sept. and the parks were empty). My only commitment was the ADRs, but I even ended up changing those times/locations twice in 5 days because we just weren't going to make it.
For our trip this fall, I have a list of restaurants that I'd like to eat at and believe my kids would enjoy (just a list with lots of options in each park; I will make dinner reservations for a few nights).
Pack as compact a day bag as possible. You will have to park the stroller for rides, so a small bag with no valuable in it will allow you to just leave the day bag.
You know the drill: Hand sanitizer, hand wipes, tissues, sunscreen, water bottles (I use soft, packable refillable ones).
3) Plan for inclement weather.
The most brilliant recommendation I have seen is for a large park of disposable ponchos used just once and tossed. I can't deal with folding up 5 wet rain jackets. Disposable ponchos it is for us!
4) Dining Plan
I have not purchased a dining plan. I did the math and it is not worth the cost for my family (even
free dining isn't worth the cost upgrade to rack rates on rooms--renting points it too good of a deal). I also can't keep up with who has used which credits. Since you have the plan, make a chart so that you can track credits. Make it super simple so that you can keep track easily.
I hope you have time to post a trip report because I want to hear all of your recommendations for having a great time at DW!
Happy Travels!