Let me hold your hand...

First and foremost, Fenris will be completely puzzled by this whole cheese racing thing and will have plenty of questions, the most simple one being "why?" because he's a broody "no fun" elf!

But on a more serious note, he's got a thing against mages. He's tamed a bit over the years, mostly due to Hawke being a mage herself and opening his eyes, but he's still rather skeptical towards them and has a hard time letting his guard down. He may be a little less eager to shoot down a mage, but no doubt he is waiting for the moment they screw up. They are a danger, he has no doubt about it, but as long as they don't cause harm (and don't cast any spells on him, good or bad) he'll be somewhat willing to let them carry on. The fact she's part of the Inquisition probably makes him even less likely to be hostile though truthfully he's got his own grudge against them for dragging Hawke into their mess but that's besides the point.

I suppose it really depends on how she'd treat him, despite his rather hard to love attitude. Naturally he'll be standoffish initially, simply because he'd need to gauge whether she's an immediate threat or not, and honestly would probably avoid her unless forced to interact. If she's not too put off by his mage-hating, moody self, they might have potential for less hostile plots, but if you think she'd not just let it slide, then there is potential for clashing, because Fenris is pretty firm in his rather discriminatory views. He'll admit that he may be a bit harsh from time to time, but he doesn't think it's without merit.

He's the sort of guy who'd probably try to make sense of a joke until it's no longer funny and I sort of imagine that's how the whole cheese thing would ever go down because he just doesn't see the appeal whatsoever! The mage has gone mad, finding humor in cheese!

Clashing is always a guarantee with strangers so she shouldn't take it too personally, he's just the type of guy who needs some warming up or at least someone with enough persistence to stick through with him. She's mostly right in her assumption though. His own experiences are the reasons why he hates them so much and since he still hasn't completely let go of the past, he's naturally still a bit averse. But clearly he's not as set in stone as he'd have you believe since he is "friends" with a couple of mages, and is in a relationship with another. Underneath all that sass and anger is a scared little elf, honestly, but he'd sooner kill a person for accusing him of such before he'd actually admit to it.

But that all aside, I agree! The best course of action would just be to toss the two toegether and let them run. Could turn out favorably, could end up with them bickering. Either way, I'm sure it'll be fun and whenever you are in the mood to thread, I can either get one started up or you can :D If nothing else they can be accidental drinking buddies!