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Thanks for the suggestions folks. Never heard of the vaseline idea - I'll try that!
We've tried cinnamon (worked pretty well one year, but not this time), cayenne (works well, but I'm not using it anymore because of the kiddo), and chalk - no luck with the chalk. We've tried the hoovering idea - these are very persistent ants. I just found a non-toxic orange-peel-based spray in the back of the broom closet, so we'll see how that does. If not, vaseline it is!