New Earth. Book 1 Wagon train to the stars - Diane Carey

Having saved Earth from the threat of V'Ger, James T. Kirk is called again to the final frontier. His new mission: to lead a valiant group of settlers to a distant world, to defend the struggling colony from alien threats, and to explore the diverse mysteries and dangers of a strange new Earth!
Far from the Federation, a newly discovered M-class world has been selected as a potential home by a group of hardy and determined colonists. Starfleet can spare only one ship to escort the would-be settlers on their perilous voyage - but that ship is none other than the legendary Starship Enterprise, commanded by the most famous captain in the quadrant. Now Kirk finds himself responsible for the lives of 30,000 men, women and children - a task that grows all the more difficult when the expedition is caught in the middle of an ancient feud between two dangerous alien races!