I'm pretty slow, too. Probably slower than you'll be going, since I'm recovering from some tendinitis in one knee! I can still give myself one hour per ten miles and be just fine.
Having lived near where you're headed a few years ago, I'd suggest keeping Brandt Road in mind as well for getting from McLoughlin to 18th; Grand can be a busy four lane road with only one side street to deal with, while Brandt is a really wide, two lane, lower traffic road, but with parallel parked cars and lots of driveways. Headed back southbound and uphill to McLoughlin, I'd suggest Brandt since the driveways and parked cars seem to be less of an issue at hill climbing speed than four lanes of 40 mph traffic!
And a note on C-Tran: As of today, the entire system has been shuffled and is starting over nearly from scratch without any transition period. And some of the routes have been combined into 40-mile round trips, so be aware that the schedules may loosely represent an abstract estimation of reality...