UPDATE 04/10/2013 - AudioLabel 5.00 (Build 6) now includes the Canon MG5450 Direct CD Printer template, so there is no need to make a custom template.
Yes, you can print directly on the disc in AudioLabel using the Canon MG5450; although, you will need to make a custom template.
Please go to the "Change Label Template" dialog and then click the "Create New" button. From there, enter "Canon MG5450" for the Name, select "Milimeters" for your Units, and also select "CD/DVD Printer" for your Paper Size. Then enter the following dimensions for the disc:
Left: 6.1 mm
Top: 60.9 mm
Outer Diameter: 118.0 mm
Inner Diameter: 41.0 mm
You should adjust the "Inner Diameter" to the actual hole size of your ink jet printable disc. Next "Save" your template and make sure it is selected in the "Change Label Template" dialog. From this point, printing should be straight forward; although, it's always recommended that you test print on a scrap disc before using the real deal.
Please let me know if you need further assistance.