I'm hoping someone can help with what I think should be quite straightforward to achieve, but it's appearing not so easy..

Basically, I have 2 Objects (I'll call them ParObject and ChldObject).  A specific field change on ParObject should trigger scheduled emails (sent in 3 hours) for ChldObjects with a specific status.

I've created a Flow on the ParObject which is triggered by the field change, and which then updates a field on the ChldObject.
And I've created a Workflow Rule on the ChldObject which picks up the field change from the Flow and sends the Email Alert (using a Timed/Scheduled action).  From what I've read Scheduled Emails can only be sent from Workflow Rules.

I can't get these flows to run correctly. 
If the ParObject flow uses an Update object a CPU limit error is shown when the field is updated by the users.
If the ParObject flow uses a Loop and Update in the loop it hits a governor limit.

I've read that Autolaunched and Screen flows can use a Wait action inside a loop which should get around the governer limits but am not sure how to create this.

Anyone created something like this previously, or got any ideas?

Thanks in advance