Saber, if the shop you're buying the bike from is a Trek dealer, then Bontrager tires may be the main brand they stock.
If so, then the Bontrager Comfort tire might be a good choice. It has a thin smooth strip down the center to reduce rolling resistance on paved surfaces and has tread on the outside edges for added traction when you're off-road riding.
If they've got those in the Hardcase version, that would be an added advantage.