There's a daily catamaran from Korcula to Dubrovnik at 7.30 am (about an hour later on Sundays) which is a lot cheaper than a private car. http://agencija-zolpp.hr/wp-content/uploads/2021/05/9808-Lastovo-Korcula-Dubrovnik-20-08.pdf
Thank you, thank you, thank you
Somehow I missed this, I was afraid we wouldn't arrive until late that night. Really appreciate your help.