Obviously everyone is different. As a kid I would have been far more afraid of the slides seeing them as they are now, but hidden I'd likely be far less scared, as I'd have no idea what I was in store for. Also as a kid I'd have been able to understand, big scary volcano = big scary rides.
I think this is a valid point. The long walk up the stairs should be a big enough clue to what you're in for as well.
I think showing the goods is also a good way to bring people in, I have no doubt that once people see the big slides, they will flock towards it.
Weirdly, the hidden coaster ending to Journey to Atlantis is the only reason I ended up going on roller coasters as a kid. I was terrified of them and had I known what it was like, there is zero chance I would have ridden it.