We start by creating a budget. Then we save as much as possible from our paycheck each week, putting the money straight in to savings, and pre-paying for things as we have enough. I'm not sure if this is what you're asking, but here's some specific ways we involved the kids in saving toward our last trip:
1. Give them options, offering to put $ in the
Disneyland jar...this way they get to invest/make sacrifices, but we don't always have to be the bad guy and say no all the time!
Examples: We can order dessert/go out to pizza tonight or put an extra $20 in the jar. What do you say?
Mom, can we do a special movie night? Sure! Should we rent a movie and buy special candy, or watch a movie on Netflix, have popcorn from home & put the extra $5-$10 in the jar? What do you think?
Hey mom & dad can we go to the pool? We could go to the pool today ($20) or go float the river for free. What do you think?
2. Let the kids collect cans/bottles (at the office or at home, from grandma and grandpa, etc.) and let them turn them in. All funds go in the jar. I work for a roofing company and in the summer water bottles are always easily found around the shop! We turn them in for a 5 cent refund.
3. Extra opportunities for chores/odd jobs at home or Grandma's house.
4. Encourage them to contribute
some of their own money to the jar (The faster we save, the faster we go!).
5. A family yard sale. ALL money goes in the jar. Eliminates the kids wanting to keep the $ from toys that were theirs...that gets complicated!
6. Any found money goes in the jar (small amounts of cash from the laundry, coins found in the car, etc.).
7. Offer Disney gift cards as gift options for special occasions throughout the year (they may not always want ALL Disney cards, so we talk about it ahead of time). This becomes their individual spending $, not for the general DLR fund.
We have done it both ways, where they contributed nothing and one trip they helped in the ways described above. By FAR the best experience was when they contributed. It gave them a sense of ownership and they LOVED being a part of things and felt so PROUD when we had enough to go. Best thing we ever did was involve the kids.
Edit to add: We also make small cuts that aren't always noticeable in order to save more, not making a big deal about it. For us, groceries is the area in our budget with most potential for savings. We make homemade cookies instead of getting expensive baked goods, make more foods from scratch, cut back on expensive junk foods, etc. We also will make small changes such as going out for a $1 soft serve vs. a $4 cone at Baskin Robin's. The kids still get a special treat and no one feels the squeeze, but there is so much spending you'll be able to cut back on if you really think creatively.