My kids were going to be partially home-schooled but we have dropped that idea and gone full-time. I have found that doing our first lesson at 7:30 in the morning has been helpful. Shortly after breakfast, my 6 year old is well rested, in a great mood and very motivated. He is very receptive to doing some of his reading and writing work. After that, he is free until about 2 pm (after his in room, alone rest time) when we do math fact (fast addition stuff). He does that on the ipad and likes it pretty well. His total structured instruction time is about 1.5 hours a day. The rest of the time he plays with his sister, builds with blocks, looks at his books and draws. He also listens to up to 4 or 5 stories on the ipad and spends a lot of time asking questions about stuff in those stories. He goes outside for two to three hours a day. We do not do formal school work during weekends. This seems to work and I am going to stick to it as a mostly non negotiable schedule. I find that if I randomly ask him to do work in the day time, he balks and gets upset. And leaving it up to when he feels like it lead to procrastination and arguments about when and what. I found that when he knows the consistent schedule of when we do things he is happier.
Maybe you and your son can draw up an agreement and then you be very firm about enforcing it? I found, having a firm schdule of when he does structured work really helped us.
I have tried asking him in the past, but it was after we had been arguing, so I need to approach it again. Although, for him, it doesn't matter what time of day it is-he is spoiling for a fight. Ugh!