Currently I'm using A Natural Primary key for a table. It's a trip code that is 10characters (alphanumeric) long. Now, I need to relate this key to another table, often times with several items being related in a one-to-many fashion. (I.e. 15 trip highlights associated to one trip code).

Would it be best just to use a simple surrogate key; i.e. a numeric ID? Once all trips are entered, the largest interger would only be four digits.