I plan to purchase a bike for my birthday to use in Colorado in the summer.  It will primarily be to toodle around town, but I also would like to use on light trails (not much elevation) and gravel roads where I think fat tires could be helpful (ie Radrover).  That being said,  I think I'd also love a feature of a second seat to carry a passenger when I use it in town like the Radrunner Plus but I am not sure if I could get a Radrover Plus and add a seat to it?  Maybe that's not even possible?

What would you recommend?  Assume 20% trail and 80% town.