Seems realistic. 1-1/4 hours may be what you start at, or at least hit pretty early on. But 14 miles can probably be done in under an hour once you get used to the route. Biking is indeed good exercise. I only do 10 minutes each way, and its enough that I can maintain my weight despite less than enviable eating habits.

Is the trail paved? This makes a big difference, and if time is an issue, many people prefer riding on roads to unpaved trails. Still, it looks like it's a rail trail, which means easy grades, so if the roads are hillier, it probably evens out.