Hello Carolee,
You can use User Agent Groups for this. In Performance>Cache Groups>Manage User Agent Groups, you can specify the group of user agents by specifying names in the user agents field. Assign a set of user agents to use a specific theme, redirect them to another domain or if an existing mobile plugin is active, create user agent groups to ensure that a unique cache is created for each user agent group. Drag and drop groups into order (if needed) to determine their priority (top -> down).
So in your case, enable the group, select pass-through in the Theme drop-down, and add the URL in Redirect users to: field that is required by the redirect plugin.
Make sure to save all settings and purge the cache after the changes are made
I hope this helps!
Thanks!