A good auger.
It will never happen and you don’t want it to. Open holes are a open invitation for disaster. Several things can happen:
1)Your house could drift in and flooding occurs through the open holes.
2) Muskrats move in, yes it does happen often
3)Warmer air coming off the water can etch holes in your banking/ice and make a “wind hole” as we call them that basically work as a snow pump for the inside of your fishouse
4) If flooding occurs on the lake you are now the proud owner of the drain holes that will grow by the minute until they get large enough to consume your house.
5)If the heat quits the open holes work better then any humidifier turning the inside of your house into a snow cone complete with freezing the door shut.
If the house is attended for the entire time you are going to have to redrill, just the way it is if not let them freeze back shut for piece of mind.