Expert WP Designer/ Developer Here!
Can use the action hooks to achieve the delay you require. Plus probably you would need a parameter in the admin where you would set the delay time.
I have heavily customized many plugins for various clients - including League Manager, Project Manager, Appointments+ for Group Class bookings, , Paypal integration, Cubepoints, DSIDXExpress, Prosperent API, Custom Fields for Buddypress etc.
Also created plugins for Advertisement Popups, many for [login to view URL] for modal login, modal registration, online appointments
I have created and customized many themes including WPCasa, Realia, Commander, Omega etc with responsive behavior.
I would be glad to provide details on these projects if required. Do check out my reviews - most of my clients on freelancer are from the US/ UK.