Drilling the old rivet with a 1/4" drill will work as long as the rivet don't spin with the drill. If it does spin the easyest thing to do is grind it off with a dremel or other grinder.
If you grind the rivet from the outside of the kettle (tail end), where the rivet was bucked (mushroomed or rounded) ((lid vents are bucked from the inside)), the metal is very thin and can be ground off way easier than grinding the head of the rivet.
If the rivet spins, and you dont have or cant borrow a grinder, as an alternative you can grab the head of the rivet with pliers or vise grips and hold it while you drill.