We have two must dos every time we go down. They are traditions.
1) Every vacation, we buy one Christmas ornament to commorate that vacation.
2) My father started the tradition on my first visit to WDW when I was a baby. I always get a piece of jewelry. When EPCOT opened, that tradition turned into pearls from Japan. Every time we go, I get one of the oysters that they dive for and have it made into something (ring, necklace, etc).
One mistake I did make recently was being talked out of the ornament for one of our vacations. Everytime I decorate the tree, I know it is missing.
Our last trip, we were married on the Disney Magic and I insisted that we not only get the vacation ornament, but one wedding/honeymoon one as well.
On that trip, we traveled with 20 family members. It was crazy to try and organize everything and since we were on the cruise, I didn't even try. We had three rules with that many people: 1) Everyone goes their own way, but meets for dinner (unless sick) 2) they HAD to dress up for Pirate Night. It's Disney, why bother if you aren't going to have fun? and 3) they had to be where they needed to be on the wedding day.
We had a blast except for my cousin who was not very organized. We had to keep reminding him to go get his passport when debarking at ports.
My father has Alzheimers now and we don't know how much longer we have him. We make the most of our vacations now and we take him with us. It is a lot less planning now. We have a wheelchair for him to go through the parks and have to make adjustments with speed and stops. We go with the flow based on him, but we don't mind. We'll always have another trip to Disney, but we won't always have him to enjoy them with. Those memories that we've made through the years with our many trips there are important. Even with his memory failing, he still remembers going on Dumbo with me as a baby, or funny things that happened in different places. We try to tell him about them if he doesn't remember. But he loves the place like a little kid.
The biggest mistake we could make is not taking him. Life is priceless. Suddenly, having to get everything in and working a plan isn't so important.