DS was dry at night about a week after day TTing. However, he stayed in nappies for a few months just in case. He had accidents maybe once a month. He's had one in the past 4 months. So it isn't completely failsafe.

We went from nappies to training pants after a couple of months. We used cloth training pants so they were still pants and big boy pants et cetera, but they were pants that meant I didn't have to worry if there were an accident. Would that be an acceptable compromise for your son?