I personally dislike drops (not even keen on the drops on Pirates of the Caribbean, though I've grown accustomed to them). I do love the tiny drops on Space Mountain, but don't much care for either drop on Splash Mountain, and California Screamin' about did me in. Not surprisingly, I have never been on Tower of Terror.
I don't personally consider anything on Indy to be a drop at all, but there is a pretty serious dip. I think the reason it doesn't bother me is because you're still part of the jeep and my stomach doesn't go anywhere!
Obviously it's up to you what to tell him. I personally would not assure your son that it's not scary or that there are no drops, because as this thread illustrates, people have vastly differing perceptions of what is and is not a drop (and of course of what is and is not scary). It took me ages to forgive my aunt for getting me to go on a roller coaster in Cedar Point by saying it wasn't scary. I believe when the car started moving she said, "I lied." Riding it as an adult I realized that no, she wasn't lying--it wasn't scary at all. But being told it wasn't scary (and then later being told that it WAS) made the ride terrifying!
I do think it is fair to say that there are no drops worse than Pirates--or perhaps you could say a bunch of people you know who have ridden dozens of times say there are no drops worse than Pirates. (That way if he DOES experience something scary, we're the liars, not you.
)
How does he feel about Star Tours? In some ways the drops on Indy are similar to those on Star Tours, with the motion simulator cars. If you make sure he's on the inside of the car, then in theory, at least, the motion should be somewhat less pronounced too.
Have fun!
