From Pearson Airport to McMaster University: Total fare $9.05 
Bus 40 or 40A from Airport, to Square One Mall in Mississauga
then transfer to:
Bus 47 (hwy 407 go bus) to McMaster

and yes, luggage is ok to bring on these.

Alternatively, if people want to go to Toronto first:
GO Bus 34 (Bramalee) goes to yorkdale $4.20
then you can take a subway to union station $2.75

and then later on, they can use this method to get from Union to McMaster:

Basically, it is $9 one way from Union Station in Toronto, to McMaster University. (or $18 round trip, but that is same day)

You basically take the GO Train to either of 2 stations (Burlington, or Aldershot), and then switch onto the 15 / 15A GO bus, to take you to the university.

Otherwise, not cited here, is that there is an express GO Bus that just takes you to the Hamilton station fairly quickly, but doesn't go to the University on the way in. You can get off before Hamilton station, and walk about 10 minutes to the university, but probably wouldn't want to with luggage.

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