
Please -- no flames -- my comment is well-intended!
DS is 11, and we've been taking him to WDW every year since he was 5. As many others have suggested, we talk, plan, play "i Spy," play "name that WDW (attraction/park/resort)" (that is, our own 20 questions game based on our WDW trips). We pass the time together as a family.
I cannot tell you how many times, and in how many places, we have seen kids (and it does seem to be boys, especially) who are utterly glued to their hand-held electronic games. They are completely disconnected to their families, completely unaware of their surroundings, and often quite upset/disgusted when it's time to -- get on the attraction, take their seat in a restaurant, eat the food that's been delivered to the table, etc. -- because it is interrupting their game. Even DS has commented, "why did he even go on the vacation?" when seeing peers react this way.
Now I do appreciate that there are plenty of kids who can reasonably do both -- have an electronic game to pass the time (and who might have reasons they really need it to help manage stress relief or something) and still be present to the vacation they are on. But if you know your child is the sort who just gets totally absorbed (and maybe it has had a negative impact on other family activities?) you *might* want to consider leaving that stuff at home.
Again -- just my thoughts.