We have a few little light up things for our kids, but our purpose is a bit different.
My kids are a little skittish about the dark, and since so many of the rides (even the little kid's ones) are dark, we found it put a bit of a damper on things for us.
A lightbulb went off for me (no pun intended) and we ended up getting some light sticks and light-up LED necklaces for them and they feel much better! Even though we are in dark places, they still have there own personal lights (which are not really bright enough to interfere with the ride/show for anyone else, btw.)
We got ours from CVS and iParty. I like the LED necklaces (and little light saber looking things) becuase they have replaceable batteries.