I have these on my MTB at the moment for use towing the baby trailer around and riding roads in the winter (just haven't gotten around to getting my off road tires back on). They are great on the pavement but you can let some pressure out and they will grip light trails perfectly fine. Kenda Kross Plus Front/Rear Slick XC Tire, 26 x 1.95"

edit: this might be a good option as well, same basic design Kenda K908 Pathfinder 26" x 1.95" Komfort Tire Blackwall