Hi, my son would not sleep through the night without being wet either. In 7 years, his diaper was dry at night only once. Yes, 7 years.
What did we do? Well, we realized it had become a bed wetting problem, so we contacted our doctor. The doctor recommended some tests (bladder size test, a few more), but they were kind of a pain in the neck to do. So I decided to set my alarm clock and wake up every two hours to take him to the bathroom. That was the real clue... I found out he is an extremely deep sleeper. I could not wake him up. I would take him to the bathroom and he could hardly stay awake to pee. Since he was 7, he was too big for me to pick him up. That's when I decided to buy a bed wetting alarm.
Just before getting the alarm, my son had his first overnight play date. He was teased by the other boy, so that really helped his motivation to solve the problem. We bought the alarm. It was one that vibrated and made a sound. My husband put a mattress in the room and every time the alarm went off, he took my son to the bathroom. It took persistance, but eventually he was going longer and longer until he finally started waking up and going on his own. Once he was good at that, we quit using the alarm. He has not had a bedwetting incident since then (it's been 4 months or more by now...)
The brain has to be trained. Somehow the alarm helps train the brain. It's good that you are starting early, but if it doesn't work, try again 6 months later. His readiness to solve this is huge and if he is not ready now, he will be later... Good luck!