I'd suggest trying the route on a weekend. Just ride in and back -- take your time. See how it feels, how long it takes, and what routes are best. Don't try to ride fast -- at about 20 kph, for example, you are working about as hard as you would if walking at a normal pace. It is easy keep that up for the required 30 - 45 minutes.

Another thought -- if you have a bike rack on your car, you could alternate -- rideing one way, then driving the other.

Paul