#1--Plan a little special time with each child. We all want to feel special and be the center of attention, even if it is only for a few minutes. While using the baby swap passes at Disneyland, I quickly realized my older children were all vying for the extra ride with Mom (or Dad). So they had to take turns carefully thinking through which ride they most wanted. Having my 7-year-old drag me onto Tower of Terror was priceless. On a cross country trip, I spent time with one child each evening. One got extra alone time with me at the motel pool. Another wanted an ice cream from the fast food restaurant adjacent to our motel. Camping is especially rewarding because their is plentiful time to spend with each child--hiking, playing a game, swinging in the hammock under the stars. Amid all the chaos, be sure to spend a few magical one-on-one time.
#2--Take pictures and actually print them out. With digital cameras we can now inexpensively takes tons of pictures. Children love cameras, so be sure to let them take a few as well (it will surprise you what they want to photograph). When vacation is over, be sure to print a few pictures out. Perhaps your child would like to make a small scrapbook or hang a collage on his wall. These make the memories last. Most of our children have a Chuck-E-Cheese picture of themselves with a relative hanging by their beds (their choice). We also hang a picture of each child in our kitchen from a recent vacation. They love looking on the computer at pictures of themselves and then choosing one that captures their special moment.
#3--Buying the right souvenir. This turns a memory into a physical object. One of my sons has an entire stuffed animal collection and he can proudly tell you where each one was acquired--the New England Aquarium, the Amana Colonies gift shop, the Grand Canyon, Mt. Rushmore, etc. My daughter has charms from various locations. My other son a stretch penny collection (notice that most of these are inexpensive). As a child I collected postcards because they were cheaper and in focus compared to a film camera's pictures. I then wrote a memory on the back, often misspelled. Probably the best quarters I ever spent. As for amusement parks, we usually let the kids play a no-lose midway game. One time my then two-year-old won a grand prize that became the focal point of the toy room for three years and is still a family favorite story.
#4--Do something new. The highlight of our Yellowstone trip for one of our children was eating at a tempanyaki restaurant. Meanwhile my other son thought Old Faithful was more extraordinary than Niagara Falls. Often I am surprised at what is a favorite, so I intentionally try to offer my kids a wide variety of experiences. The beach on a very cold day was amazing for my then three-year-old who had never seen the ocean and loved the unending "sandbox"; how about camping, a museum, or historic site (their eyes were popping at Mt. Rushmore and the Grand Canyon).
As you can see from my list, making special memories are often NOT the expensive part of vacation but are the most rewarding. So take some time to create memories that will last long after the vacation is over.