if you want to take them to an anatomy lab try asking the education in anatomy lab
(info here: http://fhs.mcmaster.ca/anatomy/index.html)

they had students come in for a presentation for take your kids to work day, that being said you have to get people to sign forms to go in i think, and they would probably need a decent amount of warning time for you to book it (...or it may already be booked when they are coming)

...however if the students are not interested in science it is NOT the place to take them, regardless of whether you want to expose them to "every option" or not...

...I know cad labs are a little...much for some people.
Did the brain bee in 9th grade, and we got to tour the cad labs during nationals. This was a group of high school students bent on careers in neurology....and even then some people were disgusted.
I'd suggest walking through a library...take them through that stock market place in the business school...if you can get into a psych lab, that might be a little better...

Could they sit in on a lecture? I've noticed most of my lecture halls are half empty at this point, lots of room for highschoolers. And it gives them a better idea of what it's actually like to be in a university level class. Maybe better for January when classes start up again?

How about pairing them with upper year students who are in programs each kid might be interested in so they can have questions answered by someone who will be honest about the subject and the work involved in getting there - but also about how much they love it.