I've only played one character with heavy armour, and that's my Nord. She doesn't use any magic. I fight with an axe and mace with her. Problem is unless you get the perk "heavy armour weighs nothing and doesn't slow you down" (she's not high enough yet) you're really slow!

I much prefer light armour to make stealthy characters.
As for your character, I'd say either could work!
Light - you can carry more stuff, you move faster and because you're going to invest a lot into the block skill, you'll absorb most of the damage with your shield anyway

but bear in mind this reply is coming from a player who predominantly uses sneak and archery.
Heavy - take much more damage! (haven't played heavy enough to comment much - sorry!)