Venice timed ticket confusion especially Doge and Correr

I understand timed tickets to St. Mark's Basilica/Museum are required. I planned to buy those but keep rest of day flexible. My intent is at some point later in the day time TBD go to the Correr, buying a ticket that then would also allow entry into the Doge Palace. Is that flexibility still possible or not advised? Should I buy specific times for all sites in advance? We are there a few days so I have some flexibility but did not want to lock in a schedule. Thanks for any recent info.