My guess is that your original purchase contract had you obtaining possession by 5pm on the date of closing. Your addendum, however, changed that provision as it gives the seller the right to occupy after closing. Generally this addendum would lay out a specific move out date for the seller, lay out a number of rules regarding their occupancy and usually would include an amount they would pay you in rent for the time they remain in the home. While it would be nice if you had the contact info for the sellers so you could coordinate directly with them when it comes time for them to move - the listing agent is under no obligation to give you that info. You will need to have your Realtor stay in contact with the listing agent and they will have to be responsible for making sure all terms are met and everyone is out on time and the home is left in good condition with all of their things removed. Hopefully all goes well with the sellers occupancy of the home and the move out goes smoothly and on time.
Hope that helps!
Kelly Gebler, Principal Broker
Cornerstone Group NW @ Keller Williams Realty