I would doubt the cramping and loose stools come from your dogs' medallions. It sounds like you are being vigilant with cleaning and, if you are using a good quality medallion, then parasites shouldn't be the issue.
Your daughter is five. Which means she is in school, yes? Which means she could be picking up things from the playground. Do you know how many people take their dogs for walks in the schoolyard never thinking about the kids playing there the next day? If there are sandboxes then I would think there are cats using the boxes as litter. In my area dogs have been banned from school yards. It doesn't stop people. They still take them there. It's a nice big open green area. And there isn't much to be done about strays using the boxes unless they are covered nightly.
Maybe your daughter has picked up a bit of a bug from one of her classmates.