There are tips all over the internet for Disney vacations. I have done several myself (here). A lot of people say the same thing over and over again (including myself) but there is just one tip I don't agree with.
One of the money saving tips that people recommend is getting souvenirs at WalMart before you leave. That way when little Suzy wants a Mickey stuffed plush you can pull your $7 one out of your suitcase that you got at WalMart and give it to her and save some cash. Same goes for when she wants that $30 Princess T-shirt.
This sounds like a good plan BUT my problem with it is that I can go to WalMart right now and buy those and give them to my kids. So can my neighbor kids that have never been to a Disney park. Does this make me a snob, probably. But I want something to show for my Disney vacation not my WalMart shopping trip.
My first trip to Walt Disney World was in 1981 when I was 5 years old. Starting that year, all the way through my late teens, I bought one Disney plush per year. It was a smaller one, about 10 inches but I have Mickey, Minnie, Daisy, Donald, Pluto, Goofy, etc. They all have memories to go with them and I remember picking out a lot of them myself, not my mom buying it at the store and giving it to me out of her suitcase. They are all still in my room at my parents house.
T-shirts follow the same thing. But do they really need a shirt they are going to grow out of in 6 months? Yes, it's cute but it won't last. I had nicer ones made online (etsy or eBay) that I saved but I have only ever bought 2 at the parks.
I didn't get several souvenirs every year I went, just a couple. No one can afford to buy thousands of dollars worth of junk for their kids.
Limit your children to an amount, even small kids will understand this if you work with them. We like to do gift cards so there is no cash to carry around.
As for a toy, let your children have the joy of picking out what they want and you get the joy of seeing their eyes light up when they carry it around. They will love it forever. My daughters first Disney plush was Squirt from Finding Nemo. She was 2 and loved that little turtle. He still lives in her room, 9 years later! I even kept the receipt. Xander never wanted stuffed animals so we saved there. He wanted swords and the like.
My recommendation for clothing is visiting the Disney outlet store at 2 of the outlet malls in Orlando. This is official Walt Disney World merchandise that didn't sell in the parks so they move it there. When my son was 5 I got him an outfit (jeans and a long sleeve shirt) for $15. Both were Disney merchandise and had Mickey on them.
It may sound awful but I just don't like the thought of pawning off a cheap toy to my kid when we could get one together and make a lasting memory. You don't have to spend a ton of money but think about the memory. Also, how long is a cheap Mickey from WalMart going to hold up compared to one that is nicer made?
I get a lot of stuff to take with me like my post here about glow sticks for the parks. But let your kids have the joy of searching the mounds of animals for just the right one, you won't regret it!