Filler for gaps in HW floor.
We have hardwood floors on the second floors that are in decent shape. They are about 3 inches wide, nearly all with gaps in between. I have read that it's best to leave the gaps there since they expand and contract with the seasons. However, with a family full of children and pets, that it not an option. Pet hair, crumbs, etc get in the cracks. And also, when something gets spilled, it damages the ceiling below. The plaster is starting to crack and chip from things spilling above.
Most practical advice would be to not allow drinks on the second floor. But hubby is not on board with that. So I need to find the most appropriate filler. Any advice would be most appreciated!