The sardines and tuna are more of a warm and fuzzy thing for the trapper than an attractant for the coon. The coons are already attracted to the feeder for corn, so bait with corn. It is cheaper, and right there in the feeder to bait the traps. No mess and no extra ant problem.
We got a 200 acre place 7 years ago. the first year we caught/hunted about 200 coons, the next about 100, then 50... We get a coon every couple of weeks now. It took a long time and persistence to get ahead of them, and we only used corn.
I have joked in the past that I bet if a sardine or marshmallow plant was to have a coon problem they would probably bait their traps corn.
and good luck.
"Man is still a hunter, still a simple searcher after meat..." Robert C. Ruark