Thanks for the question, RMcD!
The workaround would be to get rid of the Gmail app and use the default Email app that comes with the iPhone. The default app will open links only within the Covenant Eyes app if Safari is disabled. This seems to be something particular with Gmail, that links can still be opened with Safari.
Hopefully that answers your question! Let me know if it doesn't or if you have any other questions I can help with.