Maths and Physics definitely, otherwise you'll be asking yourself "what if?" when you didn't get into the course you wanted later on.
Or slogging away doing both as an adult to qualify for said course, which is about as much fun as you can have with your pants on. Trust me
.
If you've got room in your subject list it's useful to get Chem squared away so you don't have to do it in first year should you decide to do a pure science course. IME you can bluff your way through university biology without doing it in senior.
FWIW I reckon ff's got a point about doing a non-aviation course.
If you're going to the open day, hit them with some questions about what their previous graduates are Doing Now, particularly those who aren't flying for a living. If they can name a few people working in the aviation industry as managers, planners etc
and that's something you'd be happy doing if you don't end up flying, it's probably as good a choice as any. If they start looking shifty or evading the question, be suspicious.
Uni Open Days are very useful but always remember they are a sales pitch. Unis sell courses to students and students are customers, so there can be a certain amount of positive spin about their courses, academic standard, career prospects after graduation and so on. Just bear it in mind!
One other thing; looking at the RMIT site, the aviation course is actually a B App Sci (applied science) not a B Sc (science) so they don't require real maths. I'd strongly recommend you do real maths anyway in case you decide to go with the Met course or a B Sc.
Anyway, good luck with it all!