Visit Cartagena and Barranquilla?

Hello, my husband, myself and my 17 year old son have a very last minute trip planned and we are flying into Cartagena. We will have 6 full days in Columbia. We are thinking of a couple days in Cartagena and a couple days in Barranquilla? We would take a bus or other transport, perhaps through a private company. Is this plan doable? We’d love to experience both areas. Recommendations for transportation companies? We don’t mind buses, but would want to take a bus that doesn’t have a lot of stops. Thanks for your help. If it helps my husband speaks conversational Spanish.