What your doing is going to have your fish so much better than the average guy with a keeper bag hung over the side.
I use two, two litre orange juice bottles filled with fresh water in my esky and a bucket of sea water. It's icy cold at the end of the day.
Just about every fish is bled in the live bait tank and put in the esky a bit later on.
Although I have a litttle more room and can keep my food and drink in a cooler bag in the shade seperatrly.