You have a few options for this depending on what suits you and your client best.
1. Share a Link - You can Share a Link with them so they can open the AR scene in Aero on their own device in a view only mode.
2. Export USDZ - You can export a USDZ file which will allow them to view your scene on their device without using the Aero app. They can then take a video or screen capture.
3. Take Video - You can take a video directly from the Preview mode in Aero and share that with them