Why not use auditing? That's what it's there for.

Triggers are fine, depending on the circumstances - but never add them without some thought first. That code gets executed everytime a statement hits your table(s) - so use with care. If your tables really aren't used much, then no big deal.

Auditing could also show you selects, not just the DML. And also errors on sql hitting those tables (I use that a lot).