Is it possible to rent a bike right next to a bike trail (to avoid biking in city traffic and over cobblestones)? We'd enjoy biking for a couple hours during our stay in the center of Bruges, but want to do it pretty much on a dedicated bike path. I think I've read you can follow the canal all the way to Damme, and wonder if that's feasible if we usually tire after about 10 miles. Thanks for any tips!

I haven't done Brugge-Damme on bike, but it's only 6 km or so, along a straight path. You can rest in Damme before returning.
I don't see a bike rental on the outskirts of Brugge, but it shouldn't be a problem to get a bike in the center of Brugge. If you are unsure, you can walk with the bike for a bit before getting to the outskirts.
You could rent an electrical bicycle. You can turn on the battery to help you out, and can turn it off if you want to cycle without help. They are very popular here.

Brugge-Damme is a very easy 6 km long dedicated bike path along the canal (Damse Vaart).
There are enough cafés and restaurants in Damme to take a rest (a beer, a waffle, ...) before getting back on your bike for the return trip.

Bike rental 'De Ketting' is in a good location for the Brugge-Damme trail. It's near the ringway (with bike path) so you won't have to cross the city centre and the cobblestones.
The chapter 'renting/verhuur' is in English, too. Onze service ,fietsen met advies