If you did the shrimp, it would likely make the water smelly and cloudy, but a few large water changes should fix it right up.
If you're going to be home at least once a week (or even every other week), then I would go ahead and add the cories. Remind me how much ammonia you've been cycling with?
I've been cycling at 4ppm. Are the cories the hardiest or just the best to add first?