We've been taking our kids to Disney since our DS (almost 15) was an infant and truly, the best tokens for remembering the trip has always been the scrapbooks I make them. All the other "stuff" we buy, no matter how expensive, always takes a back seat to snuggling on the couch together (okay the teen doens't really snuggle like DD12, DD 11 and DS8, but he does love to look back) and reliving the memories of entire trips.
Now that they are a little older, I let them make their own (while I still do the big one of the entire trip). You could do it for your 3 and 5 year old. An 8x8 album with photos of just her? My kids LOVE that, every single trip is special. And when we're planning our next trip, like we are now...they love looking at the old albums a LOT.
If you really want to buy something, my girls still love the charm bracelet stations that are everywhere. Buy the bracelet at the first one and then pick up a charm for each day or special thing you do. We pick the glossy colorful charms, not the plastic/rubber ones, and they have lasted years. I even love mine!
Breakables that have to live on a high shelf where they don't interact with it, helping them to remember the trip? Meh.

Wouldn't be my first choice, but if you really want to, you can sure do it. It's your memory.
