Don't panic. You probably caught the one and only flea that escaped from that home. I can't see how it would be your dogs since they would have to come in direct contact with the kids.

I'm surprised you caught it! Those things can jump. They're very hard to catch and hold on to long enough to put into a bag.

I've had fleas on my pets and I only found them because one jumped on the couch on day. A quick flea bath and a spray of the couch was all it took.

I wouldn't tell the other parents either... you handled it appropriatly, nothing to tell.