A cyclocross bike is a fine choice for the type of riding you describe. It's versatile, fairly light, great on the light dirt, and with a change in tires, can be great for a long ride like a century.
I have a Lemond Poprad with road slicks and have ridden it for long rides with great success. Then I switch the tires (tires and wheels actually) and go mud whomping.
55/Rad