You can always post videos inside a Facebook group, however it will become difficult to find over time as all the posts get pushed down by the new posts. 

Inside Coaching Genie, there's a Replays area for each group where you can share your call replays. Your clients will always be able to easily find everything in one place - modules, live call schedule, replays, etc.

Relevant Article:

How do I send a replay of a live call to group members?