Great idea to focus on the airline / airport operations side of things if you ask me.
The sponsored (mentored) schemes will like it if you can talk about experiences in the industry (e.g. work experience at an airport, or even in an airline - even if its back office) - much more interesting that say, being a hockey captain, it'll give you a lot more to talk about in an interview.
For the 0 hour cadet schemes, some people could be walking in knowing nothing about the industry - the more experience you have, and the more you have to talk about the better.
Having said all that, while you're at Uni, obviously I'd get involved as much as possible with what you can, it all helps!