@SCW-Greg 

The easiest way to ensure a seamless re-integration of your smart plugs (and all of your WiFi devices) is to set up the same WiFi name and password from your previous router on the new router. By doing so, all of your wireless devices, including the smart plugs, should automatically connect to the new router since they will authenticate using the exact same credentials they already have stored for your previous router.

There is not a "group reset" feature within the Kasa Smart app; hwoever we appreciate your interest in such a feature and will gladly share it with the Kasa Smart team. You can always leave feedback directly within the Kasa Smart app under Home -> About -> Feedback.