I'm new to all of this, but just got a bunch of kits for my daughter, including the Arduino and Cloud kits. We're just about to leave the Universal Resorts tomorrow, and I had exactly the same idea, so I'd love to help you guys figure this out.
What @lujab2004 said is right about the wands. We got an interactive wand and a regular wand, and the only difference is a little glass "bulb" on the tip that must be an IR reflector. There are no active components on the wand - no batteries. When my daughter's wand's tip got scratched it stopped working well. They took the wand back to "fix" it (actually, just swapped it for a new one), and it works great now. If I do this project, I'll be putting a reflector on the end of mine.
Everyone at the park knows that at each spell spot, your wand needs to be visible to an only semi-hidden sensor (even the kids know to look for the sensor). The kids often try to point their wand straight at the sensor, but that's not necessary (and in some cases may hurt), so I'm guessing that the bulb tip is a rounded reflector.
The "sensor", I'm guessing, is both a projector of an IR beam and the reflection sensor. They probably have an IR camera sensor, and are doing some machine learning algorithm on the pattern traced by the wand (each spell has its own pattern). Each kid does the movements in a different size and at a different rate. In some cases, my daughter got a supposedly complex pattern to work just by pointing her wand (maybe the tip accidentally traced the pattern in micro movements?).
I'm still traveling, but if I get anywhere with this when I get back, I'll report back.