I only started doing daycare two months ago, so I am probably not the best one to respond to this, but I just wanted to comment on what you said about not sitting down for 12 hours and not even during naptime. I also find it busy and tiring, but I always make sure to take some time to sit with a cup of coffee or tea in the afternoon while they are sleeping and relax a bit. I try to tidy up the worst of the lunch mess while they are still sitting in their booster seats (I ignore it if they complain or sing songs to distract them), then I make sure they all go down at the same time to maximize my free time. Once they are asleep, I quickly wash up what is left of the kitchen mess and then I sit down and relax (except for today since I am baking cookies). I think it is crucial for your own sake as well as for the kids' because you can't have the energy you need if you don't have a break. I also make sure to have some periods of time during the day when the kids are free playing and I can sit and watch. I am no expert since I am new, but I would suggest trying to put your own break time on the top of the list so that you avoid the burnout.