You know your friend and hopefully his photographic skill set.
Some pros are as incompetent as the noobs described on the link Neuro posted, there are plenty of horror stories around on the web, plenty of examples of excellent work too.
You are taking a chance either way you go, you won't know how things come out until afterward.
If you are handing over your gear for him to work with, get that gear to him well in advance of the event (like a month or more) so that he is as familiar with your gear as he is with his own. Your wedding day is not the time for him to figure out your gear.
Your friend hopefully will attend and shoot as a photographer, an observer and chronicler of the event rather than a guest and celebrant.
That said, I think that any wedding photographer would do well to consider themselves an important part and parcel of the entire celebration and place themselves so with the Bride and Groom, both Mothers in Law, the wedding planner/coordinator, the Priest/Minister/Rabbi/Mullah that will be performing the ceremony.
Here's a B&H youtube vid featuring Jeff Cable, suggest you and your friend both give it a view.https://www.youtube.com/watch?v=B-Xbr6-I00w
There are sure things in that video that won't apply, but notice how strong he is about The Family and working with and for The Family.
If you do use your friend, I suggest you let him have a full set of the raws and jpgs so he can use them for self promotion.
From my own experience of only a few wedding shoots, I find myself a little removed from photographic responsibilities when I shoot for friends as a gift, I like to be a bit more in party mode.
Shooting for friends of friends for compensation is a whole 'nother matter, I go straight into Jeff Cable mode, working hard to not miss a shot, processing and delivering the product as quickly as possible.
Gear wise, you have both a 70D and a T3i available, he should carry both. Avoid lens changes. Put the 50 F/1.4 on one body, doesn't matter which, use this for anything near low light and for sure use it for the formal, wedding party group shots.
I'd want more reach and range for the zoom on the other body than what you have or the 17-55 you've mentioned.
Consider instead any among the Ef-S 18-135s, 18-200 or the EF 24-105, 28-135.