So, looking a bit more at the module and knowing you have a Pi that leaves us with the MQTT API. You can do everything in python fairly easily. Here are some ideas for you:
For the sainsmart side of things you will need a web requests library urllib
For the Cayenne side, you will need the MQTT API library
Set up a generic digital output on the dashboard and in the callback in the python code set off a web request for the corresponding relay.
Let me know how you make out with that or if you need any help!